How does a mortgage actually work?
Buying your first home is one of the biggest financial decisions you will ever make. And yet, for something so significant, the mechanics of how a mortgage actually works are rarely explained clearly. Banks hand you a glossy brochure. Comparison sites show you tables of numbers. Nobody sits down and explains what is really going on.
So let us do exactly that.
You are borrowing money to buy a property
At its most basic, a mortgage is a loan. You want to buy a home that costs, say, £250,000. You have saved a deposit of £25,000. A mortgage lender (a bank, a building society, or a specialist lender) agrees to lend you the remaining £225,000.
In return, you agree to pay that money back over a set period of time, usually between 25 and 35 years, with interest added on top.
The property itself acts as security for the loan. This is important as it means that if you stop making your monthly repayments and cannot reach an agreement with your lender, they have the legal right to repossess your home and sell it to recover what they are owed. This is why lenders take affordability so seriously before agreeing to lend you anything.
What are you actually paying each month?
Your monthly mortgage payment is made up of two parts: the capital (the loan amount itself, gradually reduced) and the interest (the cost of borrowing, charged as a percentage of the outstanding loan). Early on, most of the payment is interest; by the end, almost all of it clears capital. A £225,000 loan at 4.5% over 25 years costs roughly £135,000 in interest alone. That is not a reason to avoid a mortgage. It is simply the cost of buying now rather than saving for decades.
What is a repayment mortgage?
The standard UK mortgage: you repay capital and interest every month, and own the home outright at the end of the term, provided you keep up payments.
What is an interest only mortgage?
Monthly payments cover interest only; the capital owed doesn't reduce, and the full original amount is still owed at the end of the term. Mainly relevant for landlords with a plan to sell at term end; residential lenders require a credible repayment strategy. First-time buyers will almost certainly be on a repayment mortgage.
Fixed rates and variable rates
Fixed rate: locked-in rate and payment for a set period (2, 3 or 5 years), then moves to the lender's Standard Variable Rate (SVR, usually higher) unless remortgaged. Variable rate: tracks an external benchmark (usually the Bank of England base rate); payments move with it. Fixed rates suit most first-time buyers for early-years budgeting certainty.
What is loan to value?
LTV is loan size as a percentage of property value (for example, a £225,000 loan on a £250,000 property is 90% LTV). A lower LTV (a bigger deposit relative to price) means lower risk for the lender, which usually means better rates. There's a whole guide on this if you want the detail.
How long should a mortgage be?
Typically 10 to 35 years. Longer means lower monthly payments but more total interest; shorter means higher payments but less total interest and a faster payoff. Many first-time buyers choose a longer term then overpay (usually up to 10% a year penalty-free) as their income grows.
What happens at the end of a fixed rate deal?
The lender moves you onto their SVR (usually notably higher) unless you act. It's worth reviewing remortgage options 3 to 6 months before the fixed deal ends; an improved LTV from repayments or property growth may unlock better rates.
Do I need a solicitor?
Yes. A solicitor or licensed conveyancer handles searches, contract review, fund transfer, and Land Registry registration. Budget roughly £1,500 to £3,000 for a straightforward purchase.
A few things worth knowing
You do not have to go directly to a bank. A whole-of-market adviser accesses deals across the whole lending market, including rates not available directly to the public.
Getting an Agreement in Principle costs nothing. It's a provisional lending indication based on a soft credit check. Estate agents take AIP-holding buyers more seriously and it speeds up offers.
Your deposit is not your only upfront cost. Stamp duty, solicitor fees, survey costs, and moving expenses add up. Budget for these on top of the deposit.
Ready to take the next step?
Understanding how a mortgage works is the foundation of everything else. If you have questions about your specific situation (deposit, income, credit history, mortgage types), speaking to an adviser gets you answers tailored to you rather than generic guidance written for everyone.
This article is for informational purposes only and does not constitute financial advice. Always speak to a qualified mortgage adviser before making decisions about borrowing.