Buy-to-let mortgages explained

So you're thinking about buying a property to rent out. A buy-to-let mortgage is the loan that usually makes that possible — and it works a little differently from the mortgage you'd get on your own home. Let me walk you through the basics, minus the jargon.

What is a buy-to-let mortgage?

A buy-to-let (BTL) mortgage is a loan for buying a property you plan to rent out to tenants, rather than live in yourself. Because the lender knows the property is an investment rather than your home, it's treated as a separate type of mortgage with its own rules.

The big practical difference is that most BTL mortgages are set up as interest-only — meaning your monthly payment usually covers just the interest, and the full amount you borrowed is still owed at the end of the term. That keeps the monthly cost lower, but you'll need a plan for how the original loan gets repaid one day (for example, selling the property or refinancing). Some landlords choose a repayment mortgage instead, where you chip away at the balance over time. Both exist — which suits a given person depends entirely on their situation, and that's a conversation for a qualified adviser, not for me.

One more thing worth knowing: most straightforward BTL lending to private individuals isn't regulated by the Financial Conduct Authority in the same way a residential mortgage is. That doesn't make it risky by default, but it's a reason to go in with your eyes open.

How lenders decide what you can borrow

With a mortgage on your own home, lenders look mainly at your income. With buy-to-let, the star of the show is usually the rent. Lenders want to see that the expected rental income comfortably covers the mortgage payments, with a cushion on top — this is often called a rental cover or stress test.

In plain terms, they're checking that the numbers still work even if interest rates were higher than they are today. That's why two properties with the same price can support very different loan sizes depending on the rent they're likely to achieve.

A few other things typically come into the picture:

• Your deposit — buy-to-let usually needs a larger deposit than a residential mortgage. The exact amount varies by lender and situation.
• Your circumstances — some lenders want you to already own your own home, or to earn a minimum income, or have a certain amount of landlord experience. Others are more flexible.
• The property and the tenant type — things like flats, new-builds, HMOs (houses in multiple occupation, where rooms are let to several unrelated tenants) or holiday lets can each have their own criteria.

I'm giving you the shape of it, not figures — because the specifics change constantly and depend on you.

The costs and responsibilities to factor in

The mortgage is only one part of the picture. Being a landlord comes with running costs and duties that are easy to underestimate, so it's worth building a realistic view before you commit.

• Void periods — times when the property sits empty between tenants, but the mortgage still needs paying.
• Maintenance and repairs — boilers, safety certificates, wear and tear. Some months cost more than others.
• Tax — rental income is taxable, and the rules around what you can and can't offset have changed over the years. This is genuinely worth checking with a tax adviser or accountant, as it can materially affect the maths.
• Fees — buy-to-let mortgages can come with arrangement fees, valuation costs and legal fees, and letting agents charge for finding and managing tenants if you use one.
• Legal responsibilities — landlords have real obligations around safety, deposits and giving notice, and these differ across England, Scotland, Wales and Northern Ireland.

None of this is meant to put you off — plenty of people let property successfully. It's just the fuller cost of the thing, so nothing catches you out.

In your own name or through a company?

You may have heard of landlords buying property through a limited company rather than in their personal name. Both routes exist, and each has different implications for tax, borrowing options and admin.

This is one of those areas where the right answer genuinely depends on your personal circumstances, how many properties you hold, and your wider tax position — so it's a decision to make with a mortgage adviser and, ideally, an accountant, rather than off the back of a guide. I'm flagging it exists so you know it's a question to ask; I'm not going to tell you which way to lean, because that would be advice, and that's not my job.

Using an adviser vs going direct to a bank

You've got two broad ways to arrange a buy-to-let mortgage: approach lenders yourself, or go through a mortgage adviser (broker).

Going direct can suit people who are confident, and some lenders keep certain deals exclusively for people who come to them directly — a broker simply can't see those. So direct isn't automatically the lesser option.

A whole-of-market adviser, on the other hand, searches across a wide range of lenders rather than just one, which can be genuinely useful with buy-to-let because criteria vary so much from lender to lender. They also handle a lot of the paperwork and know which lenders tend to like which situations. The trade-off to be aware of: some brokers charge you a client fee (many are instead paid by the lender), and, as above, they won't have access to direct-only deals. A good adviser will be upfront about how they're paid before you commit to anything.

Neither route is 'the right one' — it depends on you. The point is simply to know both exist so you can choose with your eyes open.

Your property may be repossessed if you do not keep up repayments on a mortgage or other debt secured against it. This guide is general information, not advice.