Your lender will tell you the maximum you can borrow. That number is not the same as the house you can comfortably afford, and confusing the two is how buyers end up house-poor.
Why the lender's number is not your number
Lenders approve loans based on risk models, not on your lifestyle. Their maximum assumes you will spend a large share of your income on housing and debt, and it says nothing about retirement savings, childcare, travel, or the emergency fund you still need to build. A payment that looks fine on a loan application can feel crushing once groceries, gas, and real life are added back in.
That is why affordability has two separate tests: what a lender will allow, and what your budget can carry month after month without stress. The smart move is to run both, then buy to the lower of the two. You can always buy less house than the maximum; you cannot easily shrink a mortgage after closing.
The 28/36 rule, explained
The classic guideline lenders use is the 28/36 rule. The first number caps housing costs at 28 percent of gross monthly income. Housing costs here mean principal, interest, property taxes, homeowners insurance, and homeowners association dues, often shortened to PITI plus HOA. The second number caps all monthly debt payments, including housing, at 36 percent of gross income. That total includes car loans, student loans, credit card minimums, and any other required payments.
Take a household earning $90,000 a year, or $7,500 a month before tax. Twenty-eight percent of $7,500 is $2,100, so housing should stay at or below $2,100 per month. Thirty-six percent is $2,700 for all debts combined. If that household already pays $400 a month on a car loan and student loans, the housing cap under the second test is $2,700 minus $400, or $2,300. The tighter limit wins, so the housing budget is $2,100 per month.
The rule is a starting point, not a law. In high-cost cities, many buyers stretch toward 33 percent for housing; in lower-cost areas, staying near 25 percent leaves far more breathing room. Treat 28 percent as a ceiling for comfort, not a target to hit.
The costs beyond the mortgage payment
First-time buyers most often underestimate everything that is not principal and interest. Property taxes vary enormously by location and can add several hundred dollars a month. Homeowners insurance, flood insurance where required, and HOA dues add more. Then come the costs nobody escrows for you:
- Maintenance and repairs: budget 1 to 2 percent of the home's value per year. On a $350,000 home, that is $3,500 to $7,000 a year, or roughly $300 to $580 a month.
- Utilities: a larger home usually means larger heating, cooling, water, and trash bills than an apartment did.
- Lawn, pest, and seasonal work: small individually, but they recur all year.
- Furnishing and setup: the first year in a house is unusually expensive, from window coverings to a lawn mower.
Work these into the monthly picture before you shop. A $1,650 principal-and-interest payment becomes a $2,100 housing cost very quickly once taxes, insurance, and dues are added, and the maintenance reserve pushes the true cost higher still.
Worked example: turning income into a price
Return to the $90,000 household with a $2,100 monthly housing cap. Suppose taxes, insurance, and HOA dues total about $450 a month, leaving roughly $1,650 for principal and interest. At around 6.5 percent on a 30-year fixed loan, each $1,000 borrowed costs about $6.32 a month, so $1,650 supports a loan of roughly $261,000.
With a 20 percent down payment, that loan corresponds to a purchase price near $326,000. With only 5 percent down, the price is closer to $275,000, and mortgage insurance would shrink the affordable loan further. These are approximations, and your rate, tax bill, and down payment will shift them, but the method is what matters: start from monthly income, apply the 28/36 caps, subtract taxes and insurance, and only then convert the remaining payment into a loan and a price.
Also check the payment against take-home pay, not just gross pay. A $2,100 housing cost on $7,500 gross is 28 percent, but on $5,600 of take-home pay it is nearly 38 percent. If that share leaves nothing for savings, the house is too expensive at that income, whatever the lender approved.
Down payment, reserves, and the comfort test
A larger down payment lowers the loan and the payment, but draining every dollar of savings to get there is its own risk. Keep a separate emergency fund intact after closing, plus a repair reserve for the first year. Lenders call these reserves for a reason: a roof leak in month two should be an annoyance, not a crisis.
Finally, run the comfort test. Write out a full monthly budget with the new housing payment, including savings goals and the spending that keeps life enjoyable. If the budget only balances by cutting retirement contributions to zero or assuming no car repairs ever again, the house is too much. The right house is the one you can afford on a normal month, not just on a perfect one.
Frequently asked questions
Is the 28/36 rule still realistic in expensive cities?
It is still a useful ceiling, but many buyers in high-cost markets stretch housing toward 33 percent of gross income. If you stretch, do it deliberately: cut another category, keep total debt under control, and keep an emergency fund intact. Stretching on both housing and debt at once is where trouble starts.
Should I use gross or take-home pay for affordability?
Use gross pay for the lender-style 28/36 check, then repeat the check on take-home pay as a reality test. Taxes, retirement contributions, and health premiums come out before you ever see the money, so a payment that is 28 percent of gross can be close to 40 percent of what actually lands in your account.
How much should I keep in reserve after buying?
Aim to keep three to six months of essential expenses as an emergency fund, separate from your down payment and closing costs. Add a small repair reserve on top if the home is older. Buying with zero reserves turns the first broken appliance into a credit card balance.
Does a bigger down payment always mean a better deal?
A bigger down payment lowers your payment and can remove mortgage insurance, but only up to a point. Once you reach 20 percent down, extra cash often earns more as an emergency reserve or retirement savings than as a slightly smaller mortgage. Balance the payment against the safety of having cash left over.