How Much House Can I Afford? A Step-by-Step Guide
The Real Question: What's Your Maximum Safe Payment?
Most people ask "how much house can I afford?" when what they really mean is "how much monthly payment can I handle without financial stress?" These are related but not identical questions. The mortgage amount you qualify for and the amount that actually fits your life comfortably can be different numbers. This guide helps you find both.
The 28/36 Rule: A Starting Framework
The 28/36 rule is the traditional guideline financial advisors and lenders use to define a "safe" housing budget:
- 28% rule (front-end): Your total monthly housing payment (mortgage principal + interest + property taxes + homeowners insurance, often abbreviated PITI) should not exceed 28% of your gross monthly income.
- 36% rule (back-end): Your total monthly debt payments (housing + car loans + student loans + credit cards + any other recurring debt) should not exceed 36% of your gross monthly income.
These are guidelines, not laws. Lenders may approve you at higher ratios (up to 43–50% back-end DTI with strong compensating factors like excellent credit and large reserves). But the 28/36 rule reflects what's comfortable, not just what's approvable.
Worked Example: $70,000 Annual Income
Let's run the numbers for a household earning $70,000/year ($5,833/month gross):
| Rule | Calculation | Monthly Maximum |
|---|---|---|
| 28% Front-End | $5,833 × 28% | $1,633 (total housing payment) |
| 36% Back-End | $5,833 × 36% | $2,100 (all debts combined) |
If this household has $400/month in car and student loan payments, they have $2,100 - $400 = $1,700 available for housing under the back-end rule — and $1,633 under the front-end rule. The more restrictive rule (front-end, $1,633) governs.
From Monthly Payment to Purchase Price
A $1,633/month housing budget (PITI) translates roughly to:
- At 7% interest rate, 30-year fixed, 3.5% FHA down: approximately a $230,000–$240,000 purchase price (after accounting for ~$350/month in Illinois property taxes + insurance)
- At 6.5% interest rate, with 5% conventional down: approximately a $240,000–$255,000 purchase price
That range puts you squarely in Illinois's affordable market — where real inventory exists in Joliet, Rockford, Bloomington, Peoria, and similar cities.
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Get Free Analysis →The True Total Cost of Homeownership in Illinois
Your mortgage payment is only part of what you'll pay each month. Here's what to budget for on a $240,000 Illinois home (rough estimates):
| Cost Component | Monthly Estimate | Notes |
|---|---|---|
| Principal + Interest | ~$1,300–$1,450 | Depends on rate and down payment |
| Property Taxes | ~$375–$550 | Varies widely by county; included in escrow |
| Homeowners Insurance | ~$100–$150 | Illinois average ~$1,400/year |
| PMI (if <20% down) | ~$80–$130 | FHA MIP: ~$110/month on $240K loan |
| HOA Fees | $0–$400+ | Only if applicable; ask before offering |
| Maintenance Reserve | ~$200 | Rule of thumb: 1% of home value per year |
| Total Estimate | ~$2,055–$2,430 | Before HOA; on a $240K home |
Property tax rates vary by 2–3x between Illinois counties. A $250,000 home in Champaign County costs about $4,500/year in taxes; the same home in Lake County can cost $8,000+. Always verify the actual tax bill — not just the asking price — when calculating affordability.
DTI Math: What Lenders Actually Calculate
Lenders use your debt-to-income ratio (DTI) — not your take-home pay or your gut feeling. Here's the formula:
Back-End DTI = (Monthly housing payment + All monthly debt payments) ÷ Gross monthly income × 100
Example: Can They Qualify?
Maria and David earn $90,000/year combined ($7,500/month gross). They have:
- Car payment: $380/month
- Student loans: $220/month
- No credit card debt
Total non-housing debt: $600/month
Target home: $300,000. FHA loan (3.5% down = $10,500 down), estimated PITI = ~$1,950/month.
Back-end DTI = ($1,950 + $600) ÷ $7,500 = 34% ✓ (well below the 43–45% maximum)
Front-end DTI = $1,950 ÷ $7,500 = 26% ✓ (below the 28% guideline)
Result: Maria and David comfortably qualify for a $300,000 FHA purchase in Illinois.
Where Buyers Run Into Trouble
The most common reason Illinois first-time buyers get surprised by a smaller pre-approval than expected:
- Car payments are the biggest DTI killer — a $600/month car payment on a $60,000 income takes up 10% of your DTI ceiling before your mortgage is even calculated.
- Student loans on income-driven repayment plans: lenders typically use either the actual payment or 0.5–1% of the balance/month, whichever is greater.
- Co-signed loans: if you co-signed for someone else's car or student loan, that payment counts against your DTI even if the primary borrower makes all payments.
How do these numbers apply to you?
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Get Free Analysis →What $200K, $250K, and $300K Buys in Illinois
The power of Illinois's affordability becomes clear when you compare what your budget buys in different markets:
- $200,000 in Rockford: 3-bedroom ranch, 1,200–1,500 sq ft, established neighborhood. Real competition from other buyers.
- $250,000 in Joliet: 3–4 bedroom home, 1,400–1,800 sq ft, with a garage. Strong school districts available.
- $250,000 in Bloomington-Normal: Well-maintained 3-bedroom, good condition, established neighborhood near ISU or State Farm corridors.
- $300,000 in Plainfield: Newer construction possible, larger lots, part of Will County's growing suburban market.
- $300,000 in Round Lake (Lake County): Access to the Chicago metro, commuter rail available, more competition at this price point.
Explore These Markets
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