# How to calculate home affordability on a $100K income
Disclaimer: This article is for educational purposes only and does not constitute financial or mortgage advice. Consult a licensed mortgage professional or financial advisor before making any home purchase decisions.
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A $100,000 salary sounds like it should buy a lot of house. It doesn't, not the way it used to. Run the numbers with today's rates and most lenders land you somewhere between $300,000 and $400,000, and where you fall in that range depends less on your income than on your debt load, your down payment, and — increasingly — your zip code's property tax bill. Here's how to actually work out your number instead of guessing at it.
Lenders use a two-part ratio test to decide what you qualify for, and it's worth using yourself before anyone runs your credit.
The front-end ratio (28%) caps your housing costs — principal, interest, taxes, and insurance (PITI) — at 28% of gross monthly income.
The back-end ratio (36%) caps all monthly debt — housing plus car payments, student loans, credit cards — at 36% of gross monthly income.
On $100,000 a year:
The back-end number is the one that trips people up. Say you're carrying $500/month in student loans and a $350 car payment — $850 total. That leaves only $2,150 for housing, not the $2,333 the front-end math implies. Whichever ratio produces the smaller number is the one that governs your budget. Lenders will often look past this — FHA loans allow back-end ratios up to 43%, sometimes 50% with strong compensating factors like large reserves. Qualifying for that much debt and being able to live with it comfortably are two different exercises.
As of mid-2025, 30-year fixed rates have mostly sat in the 6.5%–7.0% range. That's the number that determines whether $2,333/month buys a house or a condo.
Assuming a $2,333 PITI ceiling, a 6.75% rate, and $200/month combined for taxes and insurance (which will vary hugely by location):
| Down payment | Amount down | Loan amount | P&I payment | Taxes + insurance | Total PITI | Approx. home price |
|---|---|---|---|---|---|---|
| 3% (conv.) | $10,500 | $339,500 | $2,202 | $200 | $2,402 | ~$350,000 |
| 5% | $17,500 | $332,500 | $2,157 | $200 | $2,357 | ~$350,000 |
| 10% | $35,000 | $315,000 | $2,043 | $200 | $2,243 | ~$350,000 |
| 20% | $70,000 | $280,000 | $1,816 | $200 | $2,016 | ~$350,000 |
The table flattens out at $350,000 across down payment levels because that's the ceiling this budget supports at this rate — a bigger down payment mostly frees up monthly cash flow, not purchase price. And $200/month for taxes and insurance is optimistic in a lot of places. Bump that to a realistic $400–$500/month in a mid-tax state, and you're already eating most of the $2,333 budget before principal and interest even enter the picture.
Geography does more work here than income. In Indianapolis, Memphis, or Tulsa, $350,000 buys a real 3-bedroom house. In Seattle, Denver, or Miami, it might not cover a one-bedroom condo. A $100K salary is a national number; housing markets are not national.
Putting 20% down on a $350,000 home means saving $70,000 — a serious lift on this income. But it's worth being precise about what that money actually buys you, because "avoid PMI" undersells it.
No PMI. Above 80% loan-to-value, lenders require private mortgage insurance, typically 0.5%–1.5% of the loan annually — call it $130–$390/month on a $315,000 loan. That's pure cost with zero equity benefit. Twenty percent down erases it.
A meaningfully lower payment. $280,000 at 6.75% runs $1,816/month in P&I. $332,500 (5% down on the same home) runs $2,157/month. That's $341/month, or roughly $4,100/year, that a smaller down payment permanently costs you for as long as you hold the loan.
Better negotiating position. In a competitive market, a seller comparing two similar offers will often favor the buyer who looks financially secure — and a bigger down payment is one of the few signals a seller can actually see.
A real cushion against price drops. If values fall 10% the year after closing, a 3%-down buyer is underwater immediately. A 20%-down buyer still has 10% equity — the difference between "annoying" and "can't sell without bringing cash to closing."
None of that means you should wait. Industry surveys put the average first-time buyer's down payment around 8%, and repeat buyers around 19% — most people don't hit 20%, and rent isn't free while you save toward it. The honest move is to run your budget with PMI included and see if the payment still fits, rather than treating 20% as a prerequisite.
This is where first-time buyers get surprised — the loan payment is the floor, not the ceiling, and the gap can run $500–$1,200/month or more.
Property taxes vary by state more than almost anyone expects going in. Effective rates run from around 0.28% of home value in Hawaii to over 2% in New Jersey. On a $350,000 home:
That range alone can be the difference between qualifying under the 28% cap and blowing through it.
Homeowner's insurance has gotten meaningfully more expensive in the last few years — market estimates put the national average around $2,270/year for $300,000 in dwelling coverage, or roughly $189/month. In Florida, Louisiana, or parts of coastal Texas, that number can run $4,000–$5,000+ annually, and in some wildfire- or flood-prone areas, insurers have simply stopped writing new policies. If you're house-hunting in a high-risk region, get an insurance quote before you fall in love with a house — it can change the math more than the mortgage rate does.
HOA fees, if applicable, typically run $250–$300/month nationally, but amenity-heavy communities can charge $800/month or more. This is a line item people routinely forget to ask about until after they've made an offer.
Maintenance — the rough 1% rule suggests budgeting 1% of purchase price annually, or about $292/month on a $350,000 home. Older homes, older roofs, and older HVAC systems push this higher; a home inspector's report is a better guide than a flat percentage once you're under contract.
Interest rates move affordability more than almost any other variable, including the sticker price of the house itself. Holding the $2,333/month budget constant, with no other debt and 20% down:
| Rate | Max loan amount | Home price at 20% down |
|---|---|---|
| 5.00% | ~$434,000 | ~$543,000 |
| 5.75% | ~$400,000 | ~$500,000 |
| 6.25% | ~$378,000 | ~$472,000 |
| 6.75% | ~$359,000 | ~$449,000 |
| 7.25% | ~$341,000 | ~$426,000 |
| 7.75% | ~$324,000 | ~$405,000 |
The gap between 5.75% and 7.75% is about $95,000 in purchasing power on the exact same income — roughly the price of an extra bedroom in most metros. That's why credit score work pays off disproportionately here: a borrower at 760+ typically gets a rate 0.5–1.0 points lower than one at 680, and over 30 years that spread can add up to $60,000+ in extra interest paid by the lower-score borrower. If you're six months from applying and your score is in the high 600s, spending that time paying down revolving balances is arguably a better use of energy than browsing listings.
Take a hypothetical buyer: $100K salary, $400/month car payment, no student loans, $25,000 saved for a down payment, decent-but-not-great 700 credit score, shopping in a mid-tax state.
Back-end math: $3,000 max debt minus $400 car payment = $2,600 available for housing. But the front-end cap of $2,333 is lower, so that's the real ceiling. At a 700 score, this buyer probably isn't getting the best available rate — call it 6.9% rather than 6.5%. With $25,000 down (roughly 7% on a $350,000 home), they're paying PMI, which eats another $150–$200/month out of that $2,333 budget. Net effect: their realistic purchase price is closer to $310,000–$325,000, not the $350,000 the simple version of the calculation suggests. The gap between the "textbook" number and the real number is almost entirely credit score and PMI — two things a buyer can actually influence in the 3–6 months before applying.
How much house can I afford with a $100K salary and no debt?
With zero existing monthly debt, your ceiling is the front-end limit: about $2,333/month. At 6.75% with 10% down, that's roughly $350,000–$380,000 depending on local taxes and insurance.
Can I buy a home on $100K income with student loans?
Yes, but run both ratios. A $500/month student loan payment drops your back-end housing allowance to $2,500 — though the 28% front-end cap of $2,333 may still be the binding constraint. Use whichever number is lower.
How much do I need saved before buying?
Down payment plus 2%–5% of purchase price in closing costs. On a $350,000 home at 10% down: roughly $35,000 down plus $7,000–$17,500 in closing costs — call it $42,000–$52,500 before you get keys. Keep 3–6 months of housing costs in reserve on top of that.
What credit score do I need for a good rate?
Aim for 740+ for the best conventional pricing. FHA loans open up at 580+, but often carry mortgage insurance for the life of the loan. The jump from 680 to 760 is worth actively pursuing before you apply, not after.
Is the 28/36 rule still relevant?
As a qualification threshold, less so — many lenders will approve DTIs up to 43–45%. As a personal guardrail for what you can actually live with month to month, it's still the most useful gut-check available.
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One thing to do this week: pull your free credit report and calculate your actual back-end ratio — total monthly debt divided by gross monthly income. If it's above 20%, spend the next 90 days paying down revolving balances before talking to a lender; that alone can move your rate more than shopping five different banks will. If it's under 20%, you're in reasonable shape to start pre-approval conversations, and you'll walk in already knowing your real number instead of the one a listing site guessed for you.