Short answer: using the standard 28/36 rule, a $100,000 salary supports roughly $2,333 a month in housing costs and $3,000 a month in total debt payments. At an illustrative 6.75% rate with 20% down, that buys roughly a $350,000 home — but taxes, insurance, and your other debts move that number a lot.
The 28/36 rule, step by step
Lenders use two ratios to judge affordability:
- Front-end ratio (28%): your total monthly housing cost — principal, interest, property tax, homeowners insurance, PMI, and HOA — should stay under 28% of gross monthly income.
- Back-end ratio (36%): your total monthly debt payments — housing plus car loans, student loans, credit card minimums — should stay under 36% of gross monthly income.
On $100,000 a year ($8,333 a month before tax):
- 28% → $2,333/month for housing
- 36% → $3,000/month for all debts combined
That $667 gap between the two is your non-housing debt allowance. If you have a $400 car payment and $300 in student loans, your real housing budget shrinks to about $2,300/month even though the front-end rule allows $2,333. Lenders apply both rules and use whichever gives the smaller number.
What price does $2,333 a month actually buy?
The monthly payment isn’t just principal and interest. Property taxes and homeowners insurance — which vary enormously by state and county — come out of the same $2,333. Using illustrative assumptions (6.75% rate, 30-year fixed, and combined taxes plus insurance of about 1.75% of the home’s value per year):
- With 20% down: roughly a $351,000 home — about a $281,000 loan, $1,821 in principal and interest, plus ~$512 a month in taxes and insurance, totaling ~$2,333.
- With 10% down: roughly a $320,000 home — a smaller price because the same monthly budget now also has to cover PMI.
Notice taxes and insurance eat nearly a quarter of the budget. In high-tax states like New Jersey or Illinois, the same salary buys noticeably less house than in states with low property taxes. Always estimate with your county’s tax rate, not a national average.
How your down payment changes the answer
The down payment matters twice: it reduces the loan you need, and at 20% it eliminates PMI.
| 20% down | 10% down | |
|---|---|---|
| Approximate affordable price | $351,000 | $320,000 |
| Cash needed at closing (down payment) | ~$70,000 | ~$32,000 |
| PMI | None | Required until enough equity |
Putting 20% down buys you about $30,000 more house in this example — but requires more than twice the cash upfront. That’s the real-world trade-off: the monthly math favors 20% down, while the savings timeline favors buying sooner with less down. There’s no universally right answer; it depends on how fast you can save and what prices are doing in your market.
Also remember the down payment isn’t your only upfront cost — closing costs typically add another 2–5% of the price, plus you’ll want an emergency fund left over after closing. Model the loan itself with our Loan Amortization Calculator before you commit.
Why lenders may approve you for more than you should borrow
A pre-approval is a lender’s risk calculation, not a budget recommendation. Lenders routinely approve borrowers up to 45–50% back-end ratios on some programs — well above the 36% guideline. On $100,000, that’s potentially a $4,000+/month debt load the lender considers “acceptable.”
The 28/36 rule exists because it leaves room for the life lenders don’t model: retirement savings, childcare, car repairs, medical bills, and the simple fact that a $100,000 salary doesn’t go as far in Boston as it does in Birmingham. Borrow to your budget, not to your pre-approval. A useful gut check: after the housing payment, can you still save at least 15% of your income for retirement? If not, the house is too expensive regardless of what the bank approved.
Three things that quietly shrink affordability
- Other debts. That back-end ratio is binding. Every $200 in monthly minimums on cards or loans is $200 less house you can carry.
- HOA dues. A $350/month HOA fee comes straight out of your $2,333 housing budget — equivalent to roughly $50,000–$60,000 of house price at typical rates.
- Rate changes. Affordability is extremely rate-sensitive. A one-point rate move changes the affordable price by roughly 10%. Recompute whenever rates shift meaningfully rather than relying on an old estimate.
Frequently asked questions
What house price can I afford on a $100K salary?
Roughly $320,000–$350,000 under typical assumptions (28% housing budget of ~$2,333/month, illustrative 6.75% rate, 10–20% down). Your county’s property taxes, your other debts, and current rates move this significantly — use your own numbers, not a national rule of thumb.
What is the 28/36 rule?
A traditional affordability guideline: spend no more than 28% of gross monthly income on housing costs and no more than 36% on total debt payments. Lenders use similar ratios in underwriting, though specific programs vary. It’s a ceiling, not a target — many buyers are comfortable well under it.
Does the 28% include taxes and insurance?
Yes. The “housing cost” in the front-end ratio means PITI — principal, interest, property taxes, and homeowners insurance — plus PMI and HOA dues if they apply. Forgetting taxes and insurance is the most common affordability mistake buyers make.
Can I afford a house on $100K with student loan debt?
Possibly, but the back-end ratio is what binds. If your student loans plus other minimums total $800/month, your housing budget drops from $2,333 to about $2,200 — and the affordable price falls with it. Paying down other debts before buying is often the fastest way to raise your affordable price.
Is it better to buy with 10% down now or wait to save 20%?
It depends on your market and savings rate. Waiting avoids PMI and lowers your payment, but home prices and rates may move against you while you save. Buying sooner with 10% down gets you in — with PMI you can later remove. Compare the cost of PMI against the cost of waiting a year or two in your specific market.
How accurate are online affordability calculators?
They’re decent starting points but only as good as their inputs. Most use generic tax and insurance estimates that can be far from your county’s reality. Get a local tax figure, a real insurance quote, and current rates, then run the loan through the Loan Amortization Calculator for the full picture.
Reviewed September 2026. Examples computed with the standard US mortgage amortization formula; rates and tax figures are illustrative. This article is educational content, not financial advice.