How Much House Can You Actually Afford? A First-Time Buyer's Guide
September 1, 2026
"How much house can I afford" and "how much will a lender approve me for" are two different questions, and mixing them up is how people end up house-poor. This guide walks through the ratios lenders actually apply, the costs that never show up on a listing price, and how to turn a pre-approval number into a number you'll actually be comfortable paying every month for the next 15 to 30 years.
What is the 28/36 rule, and do lenders still use it?
The 28/36 rule is a decades-old underwriting guideline: your monthly housing costs (principal, interest, property tax and insurance — often abbreviated PITI) shouldn't exceed 28% of your gross monthly income, and your total debt payments, including that housing cost plus car loans, student loans and credit cards, shouldn't exceed 36%. Most conventional lenders today will stretch past 36% — some qualify borrowers up to 43-50% total debt-to-income depending on credit score, down payment size and loan program — but 28/36 remains the benchmark for what a lender considers comfortably affordable rather than merely approvable. The gap between "what I qualify for" and "what I can comfortably afford" is usually exactly this ratio gap.
Why does a lender's maximum approval number and your real budget diverge so often?
Lenders size a loan against your gross (pre-tax) income and your debts as they exist on the day you apply — they don't know your grocery bill, your childcare costs, how often you eat out, or whether you're planning to have a second income drop when a child is born. A lender's maximum is a ceiling based on debt obligations, not a forecast of your actual disposable income. Two households earning the identical salary can have wildly different real affordability because one has $600/month in daycare and the other doesn't — the lender's formula treats them the same.
What costs does a basic mortgage calculator leave out?
A mortgage calculator's principal-and-interest number is the floor, not the ceiling, of what you'll actually pay. On top of it: property taxes (varies enormously by location — often 0.5-2.5% of home value annually), homeowner's insurance, private mortgage insurance if your down payment is under 20% (typically 0.5-1.5% of the loan annually until you hit 20% equity), HOA fees where applicable, and a maintenance reserve — the common rule of thumb is budgeting 1-2% of the home's value per year for repairs and upkeep, which people who've only rented consistently underestimate.
How much does the down payment size actually change the monthly payment?
Beyond simply financing less, a bigger down payment crosses two real thresholds: hitting 20% down eliminates PMI entirely (a direct monthly savings that doesn't build equity, it's pure insurance cost), and a lower loan-to-value ratio can also qualify you for a better interest rate tier from some lenders. On a $400,000 home, the difference between 10% down and 20% down isn't just $40,000 in financing — it's also the PMI cost on the smaller down-payment scenario, which commonly runs $100-300/month until enough principal is paid down or the home appreciates enough to reach 20% equity.
Does a 15-year or 30-year term change how much house you can afford?
It changes the monthly payment size dramatically for the same loan amount, which in turn changes what the 28/36 rule will approve you for — a 15-year term at the same rate produces a noticeably higher monthly payment for the same principal, so it can actually reduce your maximum approved home price even though you'll pay far less interest over the life of the loan. This is a real trade-off, not just a preference, and it's worth running the math both ways before deciding which term to shop for.
What's a realistic way to stress-test a home price before making an offer?
Run the numbers at a materially higher interest rate than your current quote — rates can move between pre-approval and closing — and separately, try living on your projected post-purchase budget for one to two months before you buy, redirecting the difference between your current rent and the projected new payment into a savings account. If that experiment feels uncomfortably tight, the lender's approved number was higher than your real comfortable number, and it's worth shopping in a lower price band than what you technically qualify for.