How Much House Can You Really Afford?

What the bank actually checks

Lenders lean heavily on two debt-to-income ratios. The front-end ratio caps your housing payment at a percentage of gross monthly income — often around 28%. The back-end ratio caps all your debt payments combined, including the new mortgage, at around 36% to 43%. Credit score, employment history, and down payment then adjust the offer up or down.

Notice the word gross. The bank works from income before tax, while you live on income after tax. That gap alone means the bank’s comfortable-looking ratio can feel a lot tighter once it lands in your real, post-tax budget.

Why the maximum is a ceiling, not a target

A loan sized to the maximum ratio leaves almost no slack. It assumes you want to spend the largest sustainable share of your income on housing, with little left for everything that makes a home livable. People who borrow to their ceiling often end up "house-poor" — owning a property they cannot comfortably afford to furnish, heat, maintain, or enjoy.

A useful instinct is to treat the bank’s maximum as information about what is possible, then deliberately choose a number below it that leaves room for the rest of your life and the surprises that come with owning property.

The costs the monthly payment hides

The mortgage payment is only part of the bill. On top of it sit property taxes, building insurance, and — below a certain down payment — mortgage insurance that protects the lender, not you. Maintenance is the cost people forget most: a rough rule of thumb budgets around 1% of the home’s value per year for repairs and upkeep, lumpy and unpredictable but real.

Then there are one-off costs at purchase. Closing or transfer costs commonly run 2% to 5% of the price, and a new home tends to invite spending on furniture, fixes, and higher utility bills than a smaller place. Add it all up and the true cost of ownership can be 30% to 50% more than the mortgage figure alone.

A saner rule of thumb

Many financial planners suggest keeping total housing costs closer to 25% to 28% of net (take-home) income rather than the lender’s gross-based ceiling. Build and keep an emergency fund before buying, not after, so a boiler failure or a job gap does not become a mortgage crisis.

One practical test: if you are a two-income household, ask whether you could still cover the payment on one income for a stretch. A home that only works when everything goes right is a fragile home.

Down payments, insurance, and the deposit trap

A larger down payment lowers the loan, the monthly payment, and the total interest — and in many markets, reaching around 20% lets you avoid mortgage insurance entirely. But there is a trade-off: years spent saving a bigger deposit are years of rent and of prices potentially moving. There is no universally correct answer, only the one that fits your market and timeline.

Whatever you put down, keep reserves afterwards. Lenders often want to see a few months of payments in the bank after closing, and that is good advice even where it is not required.

Stress-test before you commit

Before you fall in love with a price, run the unpleasant scenarios. If your rate is variable, recalculate the payment at a materially higher rate and see whether it still fits. Ask what happens if one income disappears for six months, or if a major repair lands in year one.

A purchase that survives those questions is one you can enjoy. A purchase that only works in the best case is a source of stress waiting for its moment.

Try the calculator

• Home Affordability Calculator — Work back from your income, debts, and down payment to a sane home purchase price using debt-to-income limits and country-specific tax assumptions.
• Loan Repayment Calculator — Work out the monthly payment, total interest, and payoff date on any loan. Add an extra-payment to see how many months and how much interest you save.
• Monthly Budget Planner — Map your monthly income and expenses, see what's left, and check it against the 50/30/20 needs/wants/savings rule.