Mortgage Affordability Guide

Quick answer

Mortgage affordability estimates how much you may be able to borrow and whether the monthly payment is realistic. It is not just about income. Deposit, debts, regular spending, dependants, interest rate, term length, and future rate changes all matter.

What lenders look at

Lenders typically consider income, employment stability, outgoings, credit commitments, loan-to-value, credit history, and affordability under different rate assumptions. The goal is to check whether the mortgage is sustainable, not just whether the first payment can be made.

Income multiples are only a starting point

You may hear simple rules such as four to five times income, but real affordability is more detailed. Two households with the same income can have very different affordability if one has childcare costs, car finance, credit card debt, or higher living costs.

Affordability examples

Real-life affordability

A mortgage should leave room for repairs, insurance, council tax, utilities, furniture, commuting, and savings. First-time buyers often underestimate the non-mortgage costs of owning a home. A payment that fits on paper can still feel stressful if the rest of the budget has no margin.

Common mistakes

• Treating the lender’s maximum as a personal budget target.
• Ignoring future rate changes.
• Forgetting maintenance and moving costs.
• Underestimating childcare or commuting costs.
• Taking on new credit before applying.
• Not testing affordability on one income if household income is at risk.

Practical stress test

Run your numbers at the expected rate, then test a higher rate and a higher monthly bills scenario. If the budget breaks under a modest change, the mortgage may be too stretched. Affordability should be about resilience, not just approval.