Getting pre-approved for a mortgage is not the same as knowing what you can actually afford. Banks will often approve you for far more than is comfortable to repay — because their job is to lend money, not to protect your financial well-being.
The standard rule of thumb in personal finance is the 28/36 rule: your monthly housing costs should not exceed 28% of your gross monthly income, and your total debt obligations (housing + all other debts) should not exceed 36% of gross income.
The 28/36 Rule Explained
The 28% front-end limit covers your PITI — Principal, Interest, Taxes, and Insurance. If you earn $7,000/month gross, that means your monthly mortgage payment (including property tax and homeowner's insurance) should stay below $1,960.
The 36% back-end limit adds all your other debts: car loans, student loans, credit card minimums, personal loans. At $7,000/month income, total debt payments should stay under $2,520. Many lenders now accept up to 43–45% back-end DTI — but that doesn't mean you should push it there.
The bank's maximum and your comfortable maximum are different numbers. Just because you qualify for a $600k mortgage doesn't mean buying a $600k home is smart.
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Beyond the Mortgage Payment: Hidden Costs
First-time buyers frequently underestimate total ownership costs. The mortgage is just the beginning. Budget for these on top of your monthly payment:
- •Property taxes (often 1–2% of home value per year, billed monthly in escrow)
- •Homeowner's insurance ($1,000–$2,500/year depending on location and home value)
- •HOA fees if applicable ($100–$1,000+/month in some areas)
- •Maintenance and repairs (budget 1% of home value per year)
- •PMI if your down payment is under 20% (typically 0.5–1.5% of loan annually)
- •Closing costs (2–5% of purchase price, paid upfront)
Down Payment Impact on Your Budget
A larger down payment lowers your monthly payment, eliminates PMI faster, and reduces total interest paid dramatically. However, putting every dollar into a down payment can leave you house-poor — without savings for repairs, emergencies, or retirement contributions.
Rule: Keep at least 3–6 months of expenses in an emergency fund after closing. Many financial advisors recommend not using retirement accounts for a down payment even if your plan allows it.
How to Increase Your Affordability
- 1.Pay down high-interest consumer debt to lower your DTI before applying
- 2.Improve your credit score (even 20 points can save 0.25–0.5% on your rate)
- 3.Save a larger down payment to eliminate PMI and qualify for better rates
- 4.Consider a longer commute or adjacent neighborhood where prices are 15–20% lower
- 5.Shop at least 3–5 lenders — rates can vary by 0.5% or more for the same borrower
Frequently Asked Questions
What is the 28/36 rule for home buying?
The 28/36 rule says your monthly housing costs should not exceed 28% of your gross monthly income, and your total debt payments (housing + car loans + student loans, etc.) should not exceed 36%. Lenders use these thresholds to decide how much mortgage to approve.
Use our Home Affordability Calculator →How much house can I afford on a $100,000 salary?
On a $100,000 salary you can typically afford a home in the $280,000–$350,000 range, depending on your down payment, existing debts, and current interest rates. Using the 28% front-end rule, your maximum monthly payment is about $2,333. With a 7% rate on a 30-year loan, that buys roughly $350,000 of home.
Calculate your exact number →What's the difference between front-end and back-end DTI ratios?
Front-end DTI (debt-to-income) covers only housing costs — principal, interest, taxes, and insurance — divided by gross income. Back-end DTI adds all recurring debt payments (car, student loans, credit cards) to that housing cost. Most conventional loans cap front-end at 28% and back-end at 36–43%.
How much savings do I need before buying a home?
Most lenders require a 3–20% down payment plus 2–5% of the loan for closing costs. On a $300,000 home with 10% down, plan to have at least $36,000–$45,000 saved. You'll also want 3–6 months of emergency funds untouched, since homeownership brings unexpected repair costs.
Check your Emergency Fund →Does a bigger down payment really lower my monthly payment significantly?
Yes. On a $350,000 home at 7%, going from 5% down ($17,500) to 20% down ($70,000) drops your monthly principal+interest payment from about $2,225 to $1,862 — a $363/month difference — and eliminates PMI, saving another $100–$200/month. The total monthly saving can exceed $500.
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