Buy-to-let runs on lender criteria. Find the broker who knows them cold.

Why buy-to-let is specialist ground

Residential mortgages ask “can you afford this?”. Buy-to-let asks a different question: does the deal stack up as a business? Lenders look first at expected rental income, then layer on their own rules about your income, experience, property type and how many mortgaged properties you already hold.

Those rules differ sharply between lenders. One is happy with a first-time landlord; another wants landlording history. One lends readily to limited companies; another only to individuals. One likes houses in multiple occupation and flats above shops; another will not touch them. A buy-to-let specialist broker carries that map in their head, and it changes constantly.

How lenders actually decide: rental cover

The single biggest difference from a residential mortgage is the interest coverage ratio, usually shortened to ICR. Rather than multiplying your salary, the lender checks that the rent comfortably exceeds the mortgage interest, with a margin, and tests it at a stressed rate higher than the rate you would actually pay.

A common benchmark is around 125% of the mortgage payment for basic-rate taxpayers and around 145% for higher-rate taxpayers, but both the percentage and the stress rate vary between lenders and with your circumstances. That variation is exactly why the same property, with the same rent, can support noticeably different loan sizes at different lenders.

Two things follow from this. First, the achievable rent matters more than your salary, so a realistic rental valuation is central. Second, if the numbers fall slightly short, some lenders offer top-slicing, using surplus personal income to bridge the gap. Not every lender does, and knowing which ones do is precisely the kind of thing a specialist knows without looking it up.

Deposit and loan-to-value

Buy-to-let deposits are typically larger than residential, commonly around 25% of the property value, though it moves with the lender, the property type and how strongly the rent covers the payments. Some lenders will consider less, others want more for specialist property types.

Worth weighing alongside the deposit: product fees on buy-to-let can be percentage-based rather than flat, and a lower headline rate paired with a large percentage fee is not automatically the cheaper deal. A broker should show you the total cost over the fixed period, not just the rate.

Personal name or limited company?

Both routes are common, and a growing number of lenders cater for company purchases (usually a special-purpose vehicle set up for holding property). Which suits you depends heavily on tax and personal circumstances, and that part belongs with a qualified accountant, not a mortgage broker and certainly not us. What a buy-to-let broker adds is the lending half of the picture:

Portfolio landlords: the four-property line

Under rules introduced by the Prudential Regulation Authority in 2017, a landlord with four or more mortgaged buy-to-let properties is treated as a portfolio landlord. Cross that line and lenders assess the whole portfolio, not just the property you are buying.

In practice that usually means providing a property schedule, a business plan, cash-flow information and sometimes an assets and liabilities statement. Some lenders stop serving landlords at that point entirely; others specialise in them. If you are approaching the fourth mortgaged property, this is the moment specialist broker knowledge stops being a nicety.

Property types that narrow the field

• Houses in multiple occupation (HMOs), often higher yielding, and a much shorter list of lenders, several of whom want landlording experience first.
• Multi-unit freehold blocks, several flats on one title, assessed differently again.
• Holiday and short-term lets, a distinct product category with its own rules on income assessment.
• Flats above commercial premises, appetite depends heavily on what the commercial unit is.
• Ex-local-authority and high-rise flats, some lenders apply floor-count or balcony-access rules.
• Non-standard construction, concrete, timber frame and steel frame each have their own lender lists.

None of these is impossible. All of them shrink the pool, and applying to the wrong lender wastes weeks and leaves a footprint. Getting it right first time is most of what you are hiring a specialist for.

First-time landlords

Plenty of lenders accept landlords buying their first rental, though criteria differ on minimum income, whether you already own your own home, and property type. Some lenders require you to be an existing homeowner; others do not. Say so honestly in the questionnaire and the brokers who put themselves forward will be ones comfortable with first-time landlords, rather than firms who discover the problem three weeks in.

Remortgaging an existing rental

The same rental-cover maths applies when a buy-to-let fixed rate ends, and the same choice appears: stay with your lender on a product transfer, or move. Because portfolio and company structures make some lenders more competitive than others over time, the broker comparison is arguably more valuable on a buy-to-let remortgage than on a residential one. Our remortgage page covers the timing side, which is identical: start early, because offers commonly last around six months.

What a broker will ask you for

• The property: address or type, purchase price or current value, and the expected monthly rent.
• Your deposit and where it is coming from.
• How you earn, and roughly what you earn, which matters for the ICR band and for top-slicing.
• Details of any properties you already own with mortgages on them.
• Whether you are buying personally or through a company, and if a company, its details.
• Anything unusual about the property or your credit history, which is far better said upfront than discovered at valuation.

Our questionnaire asks for none of this. It works in rough bands so brokers can self-select, and the detail comes later with the broker you choose.

Where a buy-to-let specialist earns their keep

• Rental cover, worked properly, whether the rent supports the borrowing you want, stress-tested the way lenders actually do it.
• Structure, how lenders treat personal versus company ownership and what that means for the products available.
• Portfolio thinking, from your first rental into portfolio-landlord territory, where everything you own is assessed.
• Awkward properties, knowing who lends on what, which saves weeks of dead ends.
• Total cost, reading percentage-based product fees against the rate rather than chasing the headline.

Anonymous until you say otherwise

Tell us the shape of the deal in rough bands, no name, phone number or email needed to see your matches. Buy-to-let specialists on our vetted panel put themselves forward against your case, you compare them side by side, and your details go only to the one broker you choose. Every broker on the panel is authorised and regulated by the FCA and vetted by us first. Broker Finder is an introducer, so advice comes from the regulated broker you pick.

Buy-to-let questions, answered straight