“How much home can I afford” is two questions wearing one coat, and a lender only answers the first. A lender calculates the largest loan it is willing to write against your income, debts and credit file. You have to calculate the payment you can carry for years, including the taxes, insurance, repairs and utility bills that arrive whether or not the mortgage is comfortable. This guide runs both calculations, using a hypothetical buyer so you can follow the arithmetic with your own figures.
Approval Is a Ceiling, Not a Budget
Underwriting is a risk opinion. It looks at gross income before tax, recurring debt payments that appear on your credit report, and the housing payment the lender will collect. It does not look at childcare, commuting costs, a 401(k) contribution, a water heater at the end of its life, or income that swings by season.
That creates two practical rules. First, treat the approval figure as the top of a range rather than the middle of one. Second, decide your monthly number before you see a price, because it is far harder to argue yourself back down after you have walked through a home you like.
Home affordability works best backwards: pick the monthly payment, subtract the non-loan costs, and let what remains define the loan and therefore the price. That is the sequence WealthTale.com uses in buyer consulting, and it is worth following even if you never hire an adviser.
Debt-to-Income: The Ratio Behind the Decision
Debt-to-income (DTI) is the main dial underwriters turn. The Consumer Financial Protection Bureau defines it plainly: your debt-to-income ratio is all your monthly debt payments divided by your gross monthly income. The CFPB also notes that different loan products and lenders set different DTI limits.
Two versions of the ratio get quoted:
- Front-end ratio. Housing costs only: principal, interest, property taxes, homeowners insurance, mortgage insurance and HOA or condo dues, divided by gross monthly income.
- Back-end ratio. The same housing figure plus every other required monthly payment (car loans, student loans, minimum credit card payments, personal loans, child support), divided by gross monthly income.
The 43% number that circulates online has a specific origin. It was the DTI ceiling written into the General QM loan definition, and the CFPB’s final rule on the General QM loan definition states that it “removes the General QM loan definition’s 43 percent DTI limit and replaces it with price-based thresholds.” Many lenders still use 43% as an internal guideline, and some programs allow more. Treat it as a reference point, not a legal line, and ask each lender you apply with what limit applies to your file.
Two things lenders will not do for you: count the costs listed below that never reach an escrow account, and judge how tight the remaining money will feel.
What a Month of Ownership Actually Costs
Meet a hypothetical buyer. Every figure here is invented for illustration. Gross household income of $9,000 a month, $600 a month in car and student loan payments, a $400,000 purchase price with 10% down, and a 30-year fixed loan of $360,000 at a hypothetical 6.00% rate.
| Monthly cost (hypothetical) | Amount | Counted in your DTI? |
|---|---|---|
| Principal and interest | $2,158 | Yes |
| Property taxes (assumed 1.1% of price) | $367 | Yes |
| Homeowners insurance (assumed $1,800/yr) | $150 | Yes |
| Mortgage insurance (assumed 0.50% of loan) | $150 | Yes |
| HOA or condo dues | $0 in this example | Yes, where they apply |
| Lender’s housing payment | $2,825 | |
| Maintenance and repairs (assumed 1% of price/yr) | $333 | No |
| Utilities (assumed) | $250 | No |
| Full cost of ownership | $3,408 |
Run the ratios on the lender’s figure and the file looks comfortable: a front-end ratio of 31% ($2,825 / $9,000) and a back-end ratio of 38% ($3,425 / $9,000). Run them on the real cost and the picture changes. $3,408 plus $600 of other debt is $4,008, about 45% of gross income, before income tax, retirement saving, childcare or groceries.
Nothing in that example is unusual. The gap is simply the two rows underwriting ignores. The maintenance and utility figures above are planning assumptions, not sourced averages, so replace them with quotes for the actual property: the age of the roof, HVAC and water heater, and the seller’s past utility bills.
Down Payment, Mortgage Insurance and Cash to Close
The CFPB’s guidance on how to determine your down payment sets out the trade-off directly. In most cases you need at least 3% down, many loan types and lenders want 5% or more, you can often save money at 10% or more, and you save the most at 20% or more. Below 20% on a conventional loan, expect mortgage insurance, which protects the lender rather than you. Ask when and how it can be removed, because the answer differs by loan type, and on some programs it does not come off at all.
Then there is the cash that never appears in the monthly payment. The same CFPB page states that closing costs, not including your down payment, typically range from 2% to 5% of the home purchase price. On the hypothetical $400,000 home, that is roughly $8,000 to $20,000 on top of the $40,000 down payment.
Reserves matter as much as the deposit. The CFPB suggests keeping the equivalent of at least three to six months of expenses in savings. A buyer who empties every account to reach 20% down has swapped mortgage insurance for a much larger risk: a $9,000 repair with no way to pay for it.
How Rates Change What You Can Buy
Interest rates move your purchasing power more than most buyers expect, because they change the loan a fixed payment supports. Freddie Mac publishes weekly national averages in its Primary Mortgage Market Survey, based on applications from borrowers with strong credit putting 20% down, so it is a reference point rather than a quote for your file.
Hold the hypothetical buyer’s principal and interest budget at $2,158 a month and change only the rate. All figures below are rounded and hypothetical, and none of them is a forecast:
| Rate (hypothetical) | P&I on a $360,000 loan | Loan a $2,158 payment supports | Price at 10% down |
|---|---|---|---|
| 6.00% | $2,158 | $360,000 | $400,000 |
| 6.50% | $2,275 | $341,500 | $379,000 |
| 7.00% | $2,395 | $324,400 | $360,000 |
One percentage point costs this buyer about $237 a month on the same loan, or about $40,000 of price at the same payment. Read that in both directions. Rates can move against you between pre-approval and contract, so leave room in your offer price. They can also move in your favor, which is an argument for knowing your payment ceiling in advance rather than deciding under time pressure.
Two habits help more than rate watching. Apply with more than one lender and compare Loan Estimates line by line, including points and fees, not just the headline rate. And avoid new credit, large unexplained deposits or a job change between application and closing.
Taxes and Insurance Vary More Than the Price Does
Two homes at the same price in two markets can carry very different monthly costs, because property taxes are set locally and insurance is priced on the specific building and location. Assessment practices, exemptions, reassessment on sale, special districts and HOA structures all differ by state and county.
Do not carry a percentage from one market into another. Instead:
- Pull the current tax bill for the exact parcel from the county assessor or tax collector, and ask whether a sale triggers reassessment.
- Get an insurance quote for the exact address, including flood or wind coverage if the property needs it, before you remove contingencies.
- For condos and HOA properties, read the budget, reserve study, rules and any pending special assessments.
- For an independent read on whether the asking price holds up against recent nearby sales, our pricing and market analysis produces a written comparable-sales review. It is not an appraisal and cannot be used for mortgage lending; your lender orders its own appraisal.
An Affordability Checklist
Work through this before you tour anything.
- Write down gross monthly household income and every required monthly debt payment.
- Choose the total housing payment you are willing to commit to, on paper, before you see listings.
- Subtract estimated taxes, insurance, mortgage insurance and HOA dues to get your principal and interest budget.
- Convert that into a loan amount at the rate you are actually quoted, then add your down payment to get a price range.
- Add maintenance and utilities to confirm the full cost still works alongside saving and everyday expenses.
- Confirm cash to close: down payment, plus 2% to 5% for closing costs, plus moving and immediate repairs.
- Confirm what is left afterwards, and keep three to six months of expenses in reserve.
- Stress-test the payment: a higher rate, an insurance increase, a special assessment, or one income pausing.
- Ask each lender what DTI limit applies and what your front-end and back-end ratios are on their worksheet.
- Decide your walk-away number and write it down, so a competitive situation does not set it for you.
If you are buying and selling at the same time, run the timing and cash flow together with seller advisory so the two sides do not collide.
Getting a Second Opinion on Your Numbers
A WealthTale.com consultant can build this budget with you, pressure-test the assumptions and put the cash-to-close figure in writing before you start touring. We advise and prepare alongside your licensed agent, lender and closing attorney or title company, who handle the transaction itself. The first consultation is free, and any fee is agreed in writing before work begins. Book a free consultation when you are ready to put real numbers on paper, or see how we pre-screen homes to buy.
