Keystone Property Finance

Keystone Property Finance | Buy-to-Let Mortgage Advice

Keystone Property Finance is a specialist buy-to-let mortgage lender focused on landlords and property investors.

At Kerr & Watson, we may consider Keystone for straightforward buy-to-let cases as well as more specialist transactions involving portfolio landlords, limited companies, trading companies, LLPs, complex corporate structures, HMOs, Multi-Unit Freehold Blocks, holiday lets, expats and mixed-use property.

Keystone can also be particularly useful where a landlord needs to refinance a buy-to-let property shortly after purchasing, carry out light refurbishment or raise additional borrowing from an existing Keystone mortgage.

Whether Keystone is suitable will depend on the applicant, property, rental income, ownership structure, existing portfolio and required borrowing.

Keystone Property Finance at a glance

Mortgage criteria and products can change, so we check Keystone’s current lending requirements before recommending an application.

Who are Keystone Property Finance?

Keystone Property Finance is an intermediary-focused specialist buy-to-let lender.

Its proposition is designed around landlords rather than owner-occupied residential mortgages.

Keystone’s lending covers both relatively conventional rental property and more specialist areas such as:

• Larger HMOs.
• Multi-unit properties.
• Complex limited-company structures.
• Portfolio landlords.
• Holiday lets.
• Expats.
• Refurbishment projects.
• Semi-commercial property.

This breadth is one of the main reasons we may consider Keystone where a transaction falls outside a conventional buy-to-let lender’s criteria.

What makes Keystone different?

Some buy-to-let lenders work best where the transaction involves:

One landlord → One SPV → One conventional house

Keystone can go considerably further than this.

Its current criteria can accommodate situations involving:

• Trading limited companies.
• LLPs.
• Layered corporate structures.
• Multiple companies.
• Intercompany funding.
• Large landlord portfolios.
• Larger HMOs.
• Larger multi-unit properties.
• Hybrid properties.
• Expats.
• Mixed-use investments.

This can make Keystone particularly relevant for professional landlords whose investment structure has become more sophisticated as their portfolio has grown.

Keystone limited company buy-to-let mortgages

Keystone has a broad limited company buy-to-let proposition.

It can lend to:

• Special Purpose Vehicles.
• Trading limited companies.
• Limited Liability Partnerships.
• Certain more complicated corporate structures.

This is a significant difference from lenders that restrict company lending to newly created SPVs using a small number of approved property SIC codes.

Trading companies

Keystone can consider qualifying trading limited companies rather than insisting the borrower is purely a property SPV.

Where the borrowing company has an existing trading business, Keystone may need additional information about:

• Company accounts.
• Bank statements.
• Trading activity.
• Directors.
• Existing liabilities.
• Purpose of the mortgage.

The property transaction still needs to make sense independently of the wider trading business.

Complex and layered company structures

One of Keystone’s stronger areas is its appetite for more complicated corporate ownership.

Its current criteria can consider:

• Layered companies.
• Holding-company structures.
• Multiple connected companies.
• Several directors and shareholders.

For example:

Individuals → Holding Company → Property SPV

may potentially be considered.

This can be useful for established landlords whose tax or succession planning has resulted in a more complicated corporate group.

The lender still needs to identify the ultimate beneficial owners and understand the complete structure before agreeing to lend.

Shareholders do not always need to be borrowers

Keystone also differs from some limited-company lenders in its treatment of shareholders.

Shareholders who are not also directors do not necessarily need to be named as mortgage applicants.

They will still be subject to relevant checks.

This can be particularly useful where a property company includes:

• Family shareholders.
• Minority shareholders.
• Non-voting shareholders.
• Succession-planning share structures.

We would normally obtain an up-to-date company structure before submitting the mortgage application.

Intercompany and shareholder loans

Keystone can consider intercompany and shareholder loans as part of the funding for a property transaction.

For example:

Trading Company Ltd → lends deposit → Property SPV Ltd

may potentially be acceptable.

This is useful because some buy-to-let lenders will only allow the deposit to come directly from the applicants or borrowing company.

Keystone will still need a clear audit trail and explanation of:

• Where the money originated.
• Which company is providing it.
• Ownership of both companies.
• Whether the money is a loan or gift.
• Any repayment terms.

Tax advice should be taken separately because mortgage advice does not determine whether an intercompany structure is tax efficient.

Incorporating an existing property portfolio

Keystone can also consider cases where an individual or partnership is moving properties into a limited-company structure.

These transactions can be legally and tax-sensitive.

The borrower should therefore take appropriate advice on matters such as:

• Capital Gains Tax.
• Stamp Duty Land Tax.
• Incorporation relief.
• Existing mortgages.
• Company ownership.

Keystone’s mortgage criteria determine whether it can finance the transaction, not whether incorporation is financially or tax appropriate.

Keystone portfolio landlord mortgages

Portfolio landlords are a core part of Keystone’s proposition.

A landlord with several properties will usually undergo additional assessment because the lender needs to understand the performance and leverage of the wider portfolio.

Keystone’s current proposition allows aggregate lending of up to £15 million, subject to underwriting and current product criteria.

This can make it relevant for professional landlords whose borrowing requirements exceed the exposure limits of smaller BTL lenders.

What does Keystone look at across a portfolio?

We may need to provide details including:

• Property addresses.
• Values.
• Mortgage balances.
• Monthly rents.
• Mortgage lenders.
• Ownership structure.
• Limited companies.
• Property types.

The lender will assess both the new property and the overall portfolio position.

A strong individual property therefore does not necessarily compensate for an unsustainable wider portfolio.

Maximum Keystone loan size

Keystone increased its maximum lending during 2025.

Its current proposition can accommodate individual property loans of up to £3 million, subject to the product, property and loan-to-value.

Its aggregate portfolio lending can extend to £15 million.

These limits are particularly relevant for larger professional landlords but should always be checked at the point of application because product limits can change.

Keystone HMO mortgages

Keystone is particularly strong in HMO mortgages.

A House in Multiple Occupation normally has several unrelated tenants who share facilities such as kitchens or bathrooms.

Specialist underwriting can be required because the lender needs to consider:

• Licensing.
• Planning.
• Number of occupants.
• Property configuration.
• Rental income.
• Landlord experience.
• Future saleability.

Keystone expanded its specialist criteria during 2026 and can now consider HMOs with up to 20 occupants.

Small and large HMOs

Keystone differentiates between more straightforward HMOs and larger specialist properties.

Smaller HMOs can access a wider range of products, while larger properties are assessed through the specialist proposition.

Keystone can currently consider first-time landlords for HMOs with up to six occupants, subject to its additional first-time landlord requirements.

Experienced landlords can potentially access the wider specialist range up to 20 occupants.

Does a Keystone HMO need a communal living room?

Not necessarily.

Keystone’s current HMO criteria do not impose a blanket requirement for a separate shared living room.

That can be important for properties where tenants have:

• Larger bedrooms.
• En-suite facilities.
• Kitchenettes.
• Shared kitchen facilities without a dedicated lounge.

The property must still comply with the relevant local authority licensing, planning and amenity standards.

Your Mortgage Bible specifically records Keystone as considering HMO layouts with en-suites or kitchenettes where they comply with council requirements.

Keystone Multi-Unit Freehold Block mortgages

Keystone also has a strong proposition for Multi-Unit Freehold Blocks, usually called MUFBs or Multi-Units.

These are properties containing several self-contained residential units held under one freehold title.

For example:

One freehold building → six self-contained flats

would generally require specialist multi-unit finance rather than six standard leasehold mortgages.

Keystone’s current specialist proposition extends to properties containing up to 20 units.

Hybrid HMO and multi-unit properties

Keystone can also consider hybrid properties.

A hybrid might contain:

• Several self-contained flats.
• One part of the building operated as an HMO.
• A mixture of room-by-room and self-contained accommodation.

These properties can be difficult with lenders whose criteria require the property to fit entirely within either an HMO or MUFB definition.

Keystone specifically identifies hybrid properties within its specialist appetite.

Shared utilities and unusual multi-unit layouts

Keystone can also consider some Multi-Unit properties where the units share utilities.

This can help with older converted buildings where separate meters were never installed.

The property still needs to provide acceptable security and comply with legal, planning and licensing requirements.

Keystone can also consider more unusual configurations that fall outside the standard criteria of mainstream BTL lenders.

First-time landlords

Keystone can consider first-time landlords, although additional restrictions apply.

For its current standard criteria, a first-time landlord will generally need at least one applicant who:

• Is aged at least 21.
• Owns their current residential home.
• Meets the relevant income requirement.
• Has satisfactory mortgage conduct where applicable.

A genuine first-time buyer with no property ownership would not normally fit the standard Keystone first-time landlord definition.

First-time landlords can potentially purchase:

• Standard BTL property.
• Smaller HMOs.
• Smaller Multi-Unit properties.

Additional rental coverage requirements can apply.

First-time landlord HMOs and MUFBs

Keystone currently accepts first-time landlords on HMOs and Multi-Unit properties with up to six occupants or units.

More specialist or larger properties generally require greater landlord experience.

This can be useful where someone already owns their home and is making their first move into a higher-yielding property rather than purchasing a conventional single-family BTL.

Keystone expat buy-to-let mortgages

Keystone can consider expat buy-to-let mortgages.

Its current proposition includes:

• Employed expats.
• Self-employed expats.
• Retired expats.
• Personal ownership.
• Limited companies.
• LLPs.

The applicant will normally need an established UK connection and credit footprint.

Self-employed and retired expats

Self-employed and retired expats are specifically noted within both Keystone’s current criteria and your Mortgage Bible.

This can differentiate Keystone from lenders that restrict their expat proposition to employed applicants working for large multinational companies.

Self-employed expats generally need stronger existing UK landlord experience and appropriate business accounts.

Retired applicants need sufficient qualifying pension income.

Expat property experience

Keystone does not normally use its expat range for someone making their first ever move into buy-to-let.

Current criteria generally require an expat to already have UK BTL experience.

Self-employed expats are subject to additional experience requirements.

This means an applicant may fit Keystone’s UK-resident first-time landlord criteria but not its expat proposition.

UK credit footprint for expats

Keystone requires expat applicants to retain an active UK credit footprint.

It also currently requires:

• A UK bank account.
• A UK correspondence address.
• UK tax reporting or declared UK income where applicable.

The applicant’s country of residence must also fall within Keystone’s acceptable-country requirements.

Keystone holiday let mortgages

Keystone offers a specific proposition for holiday lets.

Short-term holiday letting differs from a conventional AST because the occupants change regularly and rental income may vary significantly throughout the year.

Keystone can consider holiday lets for:

• Individuals.
• Limited companies.
• LLPs.
• Qualifying expats.

Holiday let experience and income

Keystone’s current holiday-let criteria require qualifying applicants to have previous property investment experience.

A minimum background income also applies.

The property must normally be:

• Fully furnished.
• Available for short-term letting for a sufficient part of the year.
• Suitable for conventional residential occupation.
• In an acceptable location.

The precise rental assessment and current maximum LTV should be checked before applying.

Airbnb and short-term letting

A property being advertised through Airbnb does not in itself determine whether the mortgage is acceptable.

We would establish:

• Intended occupancy.
• Lease restrictions.
• Planning.
• Local authority rules.
• Property type.
• Rental assessment.
• Applicant experience.

Where the intended use meets Keystone’s holiday-let criteria, a short-term-let strategy can potentially be considered.

Keystone early and day-one remortgages

Keystone is also useful for landlords who need to refinance shortly after purchasing a property.

Many BTL lenders expect the borrower to have owned a property for at least six months before remortgaging.

Keystone can consider a remortgage within six months where:

• Bridging finance funded the original purchase; or
• The property was purchased using cash and the borrower can evidence the source of funds and wealth.

This can make Keystone relevant as an exit route from short-term finance.

Remortgaging after refurbishment

Keystone can also consider an early remortgage where refurbishment work has been carried out.

Where a property is refinanced within six months, borrowing can be considered against the evidenced project costs subject to the lender’s normal maximum LTV.

The valuer will need details of the work completed.

This is important because a significant increase in property value shortly after purchase needs to be properly explained and evidenced.

Keystone Refurb to Let

Keystone also offers a specific Refurb to Let proposition.

This is designed for landlords purchasing or refinancing a property that requires relatively light improvement before being retained as a longer-term rental investment.

The initial short-term facility currently runs for six months.

What works can Keystone Refurb to Let fund?

The proposition is intended for light refurbishment rather than major development.

Examples can include:

• Redecoration.
• New kitchens.
• New bathrooms.
• Fixtures and fittings.
• General modernisation.

The refurbishment budget cannot normally exceed the lender’s permitted proportion of the initial property value.

Structural development requiring extensive planning would generally need another type of finance.

Converting a property into an HMO

Keystone’s Refurb to Let proposition can also be used where a conventional property is being converted into a small HMO with up to six occupants.

The planning and licensing position needs to be acceptable.

Once the work is complete, the borrower can potentially move onto one of Keystone’s longer-term Refurb Exit products, subject to underwriting and valuation.

This provides a possible route from:

Purchase → Refurbishment → Long-term BTL mortgage

within the same lender proposition.

Keystone semi-commercial mortgages

Keystone expanded into semi-commercial lending in 2026.

Semi-commercial property contains both residential and commercial elements.

Examples could include:

• A shop with flats above.
• An office with residential accommodation.
• A restaurant with flats.
• Other mixed-use investment property.

Keystone’s current range can finance both the residential and commercial elements within one mortgage.

Keystone semi-commercial criteria

Under Keystone’s current semi-commercial proposition:

• The residential element must represent more than 50% of the overall property value.
• Experienced landlords are required.
• Individuals and qualifying company structures can apply.
• Standard residential units, HMOs, MUFBs and holiday lets can potentially form the residential element.

Keystone currently accepts several ownership structures, including:

• Individuals.
• SPVs.
• Trading limited companies.
• LLPs.

The affordability assessment is principally driven by the residential rental income.

Properties above or next to commercial premises

Your Mortgage Bible specifically records Keystone as being able to consider residential investment property adjacent to or above commercial premises.

This is consistent with Keystone’s broader specialist property appetite.

The valuer will assess whether the commercial use affects:

• Noise.
• Smell.
• Access.
• Insurance.
• Rental demand.
• Future saleability.

A flat above a professional office can therefore be viewed differently from a property above a late-night takeaway or nightclub.

Keystone product transfers

Existing Keystone borrowers can access product-transfer options as their mortgage deal approaches expiry.

A product transfer allows the customer to remain with Keystone and move onto another available mortgage product rather than completing a full remortgage to another lender.

Eligible cases appear to brokers before the existing product reaches its reversion date.

A product transfer can reduce the administrative work involved compared with changing lender.

Keystone Product Transfer Plus

A particularly useful feature of Keystone’s proposition is Product Transfer Plus.

This allows an existing customer to:

Switch product + raise additional borrowing

without completing a conventional remortgage to another lender.

The additional borrowing is subject to:

• Current property value.
• Rental income.
• Loan-to-value.
• Credit criteria.
• Underwriting.

Current criteria allow additional borrowing up to higher LTVs on standard property, with lower maximums applying to specialist properties.

Why might Product Transfer Plus be useful?

A landlord may want to raise money to:

• Purchase another BTL property.
• Fund a deposit.
• Refurbish another property.
• Restructure their portfolio.
• Release accumulated equity.

Instead of remortgaging away from Keystone, Product Transfer Plus may allow them to retain their existing lender while increasing borrowing.

We would still compare this with a full remortgage because another lender could provide a more appropriate overall solution.

Keystone and specialist property

Keystone’s property appetite can also include cases that may not fit more conventional BTL lenders.

Examples include:

• Properties above commercial premises.
• Larger HMOs.
• Large Multi-Unit properties.
• Hybrid HMOs/MUFBs.
• Multiple kitchens.
• Shared utilities.
• Some smaller units.
• Semi-commercial property.
• Holiday lets.

Final acceptability remains subject to valuation.

Consumer Buy-to-Let

Keystone does not currently accept mortgages classified as Consumer Buy-to-Let.

This can be important where someone is renting out a property that was previously their own home.

A former residence is not automatically Consumer BTL in every circumstance.

However, Keystone’s criteria require applicants remortgaging a former residence to have relevant existing buy-to-let experience and to meet its non-regulated lending requirements.

Where a transaction is Consumer BTL, another lender will normally be required.

When might Keystone not be the right lender?

Keystone has broad specialist criteria, but it will not suit every landlord.

Another lender may be more appropriate where:

• You require a residential mortgage for your own home.
• The transaction is Consumer Buy-to-Let.
• You are a genuine first-time buyer with no existing property ownership.
• The property’s rent does not meet Keystone’s affordability calculation.
• The ownership structure cannot be satisfactorily evidenced.
• An expat applicant cannot demonstrate the required UK connections.
• A property falls outside Keystone’s security appetite.
• Another lender provides a lower overall mortgage cost.

A specialist lender should be used because its criteria provide a genuine advantage, not simply because the case could be placed there.

What we check before recommending Keystone

Before recommending Keystone, we normally establish:

• Property value.
• Rental income.
• Required mortgage.
• Deposit or equity.
• Existing property ownership.
• Landlord experience.
• Wider portfolio.
• Credit history.
• Income.
• Property type.
• Proposed tenancy.

For a limited-company application, we additionally look at:

• Company type.
• Directors.
• Shareholders.
• Ultimate beneficial ownership.
• Holding companies.
• Connected businesses.
• Deposit source.
• Intercompany funding.

For an HMO or MUFB, we also consider:

• Number of occupants or units.
• Planning.
• Licensing.
• Property configuration.
• Rental valuation.
• Landlord experience.

This enables us to establish whether Keystone genuinely fits before an application is submitted.

Do you have to use Keystone Property Finance?

No.

Kerr & Watson is an independent, whole-of-market mortgage brokerage, so we can compare Keystone with other suitable buy-to-let lenders.

Keystone can be particularly strong for professional landlords, complex companies, larger HMOs and Multi-Unit properties.

However, another lender may provide a more appropriate rental calculation, property policy, company criteria or overall mortgage cost.

Our role is to identify which lender and mortgage provide the most suitable overall solution for your circumstances.

Speak to a mortgage adviser about Keystone Property Finance

If you are considering Keystone for a buy-to-let mortgage, limited company, portfolio, HMO, MUFB, holiday let, refurbishment project or semi-commercial property, we can review the transaction before you apply.

We can assess the property, rental income, portfolio and ownership structure before comparing Keystone with other suitable lenders. Speak to an Adviser

Lender criteria, affordability calculations, product availability and lending terms can change. The information on this page is intended as a general guide and should not be relied upon as confirmation that a lender will accept a particular application or that a particular mortgage or finance product will be suitable for you.

The information on this page does not constitute personalised mortgage advice or a recommendation. The regulatory status of a mortgage or loan depends on the type of transaction and your circumstances. Many buy-to-let and commercial mortgages, and some bridging loans, are not regulated by the Financial Conduct Authority. Your home or other property may be repossessed if you do not keep up repayments on a mortgage or other loan secured against it.

Your Mortgage In 3 Easy Steps…

Conversation

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Schedule a call to speak to a mortgage adviser about your circumstances, borrowing requirements and property plans.

Alternatively give us a call on 01252 224620 or email us on info@kerrandwatson.co.uk.

Research

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We will use the information you’ve provided to research suitable mortgage options across the market and explain our recommendation to you.

If you need an Agreement in Principle, we can also arrange this as part of the process.

Application

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Once you’re ready to proceed, we will submit the full mortgage application and supporting documents to the lender.

We will liaise with the lender and its underwriters, respond to any additional requirements and keep you updated until the mortgage offer is issued and through to completion.

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