How Much House Can You Afford on $100K in St. Louis at 7%?

The Math: $100K Salary → $273K–$354K Home

Lenders start from your gross monthly income — $8,333 on $100,000 — and apply two limits: what your housing payment can be, and what all of your debts together can be. The low end of the range keeps your full payment at 28% of gross income. The high end is what most lenders would approve at a 43% total debt-to-income ratio, assuming about $550 a month in other debts (car, student loans, credit cards).

All figures use the assumptions listed in How these numbers are calculated below.

Your Monthly Payment on a $315K Home

Here is the full payment on a $315,000 home — the middle of your range — with conventional, 5% down:

That is 32% of your gross monthly income. It doesn’t include utilities or maintenance — plan on 1–2% of the home’s value per year, or about $262–$525 a month, for upkeep.

$100K: Conventional Loans and the St. Charles Tax Advantage

Most $100K buyers use a conventional loan. With 5% down you'll pay private mortgage insurance (PMI), but unlike FHA it can be removed once you reach 20% equity — by request at 80% loan-to-value, and automatically at 78% under federal law. With 10% down or more, PMI drops further. And assistance isn't off the table: $100K is under MHDC First Place's 2026 limit of $113,500 for a 1–2 person household — see the MHDC strategy below.

The biggest monthly difference between your options is property tax. St. Charles County's 0.92% rate vs. 1.12% in South County is about $54 a month on a $325,000 house — more than $640 a year, every year.

The trade-off is distance. St. Peters, O'Fallon and Wentzville put more space and newer construction in your budget, but for jobs in Clayton or downtown, the I-70 or I-64 commute is a real cost in time and fuel.

Stretching $100K Further: MHDC Assistance Plus a Seller-Paid Buydown

A $100K household is under MHDC First Place’s 2026 St. Louis income limit ($113,500 for 1–2 people; $130,525 for 3+). That means you can often stack two kinds of help: MHDC cash assistance (up to 4% of the first mortgage) goes toward your down payment, and a seller concession you negotiate in the offer pays to buy down your interest rate. Here is what that looks like on a $315,000 home with a 3% seller concession ($9,450):

Which buydown? The 2-1 buydown gives you the bigger break — about $384 a month in year one — while you settle in, but lenders qualify you at the full 7% rate, so it doesn’t raise your budget. The permanent buydown saves less each month (about $156) but lasts for the life of the loan and raises what you can be approved for.

Watch the lender fees. MHDC lets lenders charge an origination fee of up to 1% on these loans, which can make the 4% work out closer to 3%. Ask: “After your fees, how much of the 4% actually reduces my cash to close?”

Making it work: ask for the concession in your offer — with less than 10% down, conventional loans cap seller contributions at 3% of the price, which is exactly what’s modeled here. MHDC requires its written approval for buydowns on First Place loans, so have your MHDC-approved lender confirm the structure (for First Place or Next Step) before you write the offer. MHDC sets its own rate daily and it may be below 7%; these numbers use 7% to stay conservative. Purchase-price limits apply: $566,354 for a single-family home under First Place outside targeted areas, $692,211 under Next Step or in targeted areas. See our MHDC guide for the full rules.

Where $100K Lines Up With Recent St. Louis Sale Prices

These are the highest-volume ZIP codes where the median sale price falls within reach of a $100K budget, based on 7,006 residential sales in 2025–2026 (MARIS MLS; excludes new construction and condos). A median is a midpoint — every area has homes above and below it.

About this data: The prices and market numbers here come from 7,006 MARIS closed sales across 79 St. Louis-area ZIP codes, 2025–2026. They don’t reflect price changes since then. I’m refreshing this data at the end of 2026 and every six months after that.

St. Charles County leads your list: St. Peters, O'Fallon, St. Charles and Wentzville all sit between your comfortable and stretch numbers, and all benefit from the 0.92% tax rate. On the south side, 63129, Arnold and Affton line up with your comfortable budget, and Mehlville falls below it — at $100K those are areas where you can buy without stretching. Concord/Tesson and Fenton (Rockwood schools) sit above your comfortable number.

School districts follow addresses, not ZIP codes — always verify the district for a specific property. See the St. Louis school district guide.

How Your Debts Change the $100K Number

Every dollar of monthly debt payment is a dollar lenders won’t let you spend on housing. On $100K with conventional, 5% down:

An extra $500 a month in payments — a second car, say — costs you about $58,000 in buying power. Paying one off before you apply works the other way.

Cash You’ll Need to Close on $315K

Sellers can contribute toward closing costs, and lenders and assistance programs may offer credits — ask before assuming you need the full amount in cash. Keep an emergency fund after closing.

Example: $100K Household With Childcare

Illustrative example, not a client story. Two earners make $100,000 combined, have a $550 car payment, and spend $1,200 a month on daycare.

• Lender's view: approval up to about $354K. Daycare doesn't count as debt.
• Real budget: with $1,200 of daycare, the comfortable number — about $273K — is the one to plan around, at least until daycare ends.
• Payment at $315K: about $2,697 a month with 5% down, including PMI.
• Cash to close at $315K: about $25,200 with 5% down, or $40,950 with 10% down.

Mistakes $100K Buyers Make

Ignoring the tax gap. The same $325K costs about $54 a month more in South County than in St. Charles County. Factor it into your comparison.

Not planning to remove PMI. Mark the date you'll reach 20% equity and ask your lender to remove PMI then — it won't always happen on its own until 22%.

Buying to the lender's limit because "we make six figures." At $354K, the payment is about 36% of gross income before daycare, retirement savings or college savings.

Underestimating the commute. An extra 30 minutes each way is about 250 hours a year.

$100K Affordability Questions

How much house can I afford on $100K in St. Louis?

About $273K comfortably and up to about $354K with typical debts, using a conventional loan with 5% down at the rate assumed on this page.

Is St. Charles County cheaper than South County?

On property taxes, yes: 0.92% vs. about 1.12%, or roughly $54 a month on a $325K home. Median prices in St. Peters and O'Fallon are similar to South County's 63129.

Do I need 20% down on a $100K salary?

No. Conventional loans allow 3–5% down with PMI, and PMI can be removed once you reach 20% equity.

Can I combine MHDC assistance with a seller-paid rate buydown?

Often, yes: MHDC cash assistance can cover your down payment while a seller concession pays for a rate buydown. MHDC requires written approval for buydowns on First Place loans, so have your MHDC lender confirm before you make an offer; lender fees can also trim the 4%. On a $315K home with a 3% seller concession, cash to close can drop from about $25,200 to about $10,755.

How These Numbers Are Calculated

• Interest rate: 7% on a 30-year fixed loan, in line with the market as of October 2, 2026. Your rate depends on credit, loan type and the market on the day you lock.
• Property tax: 1.12% of the price for the budget range and payment table (common in St. Louis County); the area table shows each ZIP’s rate.
• Insurance: about 1% of the home’s price per year. Missouri premiums vary widely — get quotes early.
• Mortgage insurance: FHA 0.55% per year plus 1.75% upfront (financed); conventional PMI estimated at 0.60% with 5% down and 0.40% with 10% down.
• Limits: comfortable = total housing payment at 28% of gross income; lender maximum = 43% total debt-to-income, minus the other debts stated.
• Closing costs: estimated at 3% of the price.
• MHDC + buydown scenario: MHDC cash assistance at 4% of the base loan; MHDC rate assumed at the same 7% (conservative); 3% seller concession; 2-1 buydown cost = the payment difference over two years; permanent buydown at roughly 0.25% per discount point (pricing varies daily); optional lender origination fee up to 1% of the loan; 2026 St. Louis MHDC income and purchase-price limits.
• Area data: median sale price, days on market and first-weekend sale rate from 7,006 residential sales, 2025–2026, MARIS MLS.

The Bottom Line on $100K in St. Louis

On $100,000, plan around $273K, with approval possible up to $354K. Your choices widen to St. Charles County's newer suburbs and lower taxes, South County's established neighborhoods, and the edges of Rockwood schools in Fenton. Compare the full monthly cost — taxes, PMI and commute — and plan from the day you close to remove PMI.

Other incomes: $50K · $60K · $70K · $80K · $120K · $150K · $200K · Income needed by price

George Kindler

Marine Corps Veteran • Licensed Missouri Agent • 13 Years • 250+ Transactions

I work with first-time buyers making $50K-$100K every week. I know what you can actually afford, what neighborhoods fit your budget, and how to get you in a house without being house-poor. Let's talk.

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