“How Much House Can I Actually Afford?” — How Marcus Finally Got a Real Answer

Marcus had been asking himself that question for eight months.

He'd browsed Zillow, attended two open houses, and sat through one lender pre-qualification call that left him more confused than when he started. The lender told him he was approved for up to $420,000. His gut said that number felt too high. But he didn't have a number of his own to push back with.

So he spent a Saturday afternoon doing something he should have done months earlier: running the actual math himself, before talking to anyone who stood to earn a commission on his answer.

The number lenders give you vs. the number you can live with

The lender's $420,000 approval wasn't wrong. It was just the maximum — the ceiling of what the bank would lend him based on his income and credit. It said nothing about what Marcus could afford comfortably, what monthly payment would let him still save for retirement and take a vacation once in a while, or what would happen to his budget if his income dropped 15% for a year.

Those were different questions. And they started with his own numbers, not the bank's.

Marcus made $82,000 a year — $6,833 a month gross. He had $55,000 saved, of which he wanted to keep $12,000 as an emergency fund. That left $43,000 available for a down payment and closing costs.

He opened the mortgage calculator and started there.

Step 1 — What does a given purchase price actually cost per month?

Marcus entered his numbers for a $360,000 home — below his approval ceiling, but in the range he'd been browsing:

• Purchase price: $360,000
• Down payment: $35,000 (roughly 10%)
• Loan amount: $325,000
• Interest rate: 6.8% (current market)
• Term: 30 years

Monthly payment (principal + interest): $2,121.

But that wasn't the real number. He added the costs lenders often exclude from their headline figure:

• Property tax (estimated at 1.1% annually): $330/month
• Homeowner's insurance: $120/month
• PMI (required below 20% down, ~0.7%): $190/month

True monthly housing cost: $2,761. That was 40% of his gross income. More than he'd expected.

Step 2 — What does the 28/36 rule say?

The standard lender guideline — the 28/36 rule — says your monthly housing costs shouldn't exceed 28% of gross income, and total debt payments shouldn't exceed 36%.

Marcus's gross monthly income: $6,833.

• 28% housing ceiling: $1,913
• 36% total debt ceiling: $2,460

His $2,761 housing cost blew past both thresholds. He opened the DTI calculator to run it properly. His existing debts: $380/month in student loan payments, $290/month for his car.

• Front-end DTI (housing only): $2,761 ÷ $6,833 = 40.4%
• Back-end DTI (all debt): ($2,761 + $670) ÷ $6,833 = 50.2%

Most conventional lenders cap back-end DTI at 43–45%. At 50%, Marcus wouldn't just be uncomfortable — he'd likely struggle to get approved at all despite the pre-qualification number.

Step 3 — Running the scenarios

Marcus spent the next hour adjusting the inputs. He ran four scenarios, varying purchase price and down payment, to find where his DTI landed in a range he could actually live with.

Scenario 1 — $360,000, 10% down ($35,000)

• Monthly P&I: $2,121
• True housing cost with taxes/insurance/PMI: $2,761
• Front-end DTI: 40.4% — too high

Scenario 2 — $320,000, 10% down ($32,000)

• Monthly P&I: $1,857
• True housing cost: $2,477
• Front-end DTI: 36.2% — still above guideline

Scenario 3 — $300,000, 13% down ($39,000)

• Monthly P&I: $1,727
• True housing cost: $2,237
• Front-end DTI: 32.7% — within range

Scenario 4 — $300,000, 20% down ($60,000)

• Monthly P&I: $1,568
• True housing cost: $1,988 (no PMI)
• Front-end DTI: 29.1% — comfortable

Scenario 4 required $60,000 down — more than he had available right now. But Scenario 3 at $300,000 with 13% down put him in a workable position: front-end DTI under 33%, no need to drain his emergency fund, and a monthly payment he could absorb if his income dipped.

He had his number. Not $420,000. Not a gut feeling. $300,000 — arrived at through four calculations.

Step 4 — The question he almost forgot to ask

Marcus had been thinking about this as a buy decision. He hadn't seriously run the rent comparison.

He was paying $1,650/month in rent. His lease was up in four months. The rent vs. buy calculator asked him how long he planned to stay.

He entered five years — his honest answer, not the optimistic one.

At five years with a $300,000 purchase:

• Estimated equity built: $41,000 (principal paydown + modest appreciation)
• Total ownership costs over 5 years (mortgage, tax, insurance, maintenance): $168,000
• Total rent cost over 5 years at $1,650/month with 3% annual increases: $105,700

Buying would cost him about $62,000 more over five years on a cash basis — but he'd walk away with $41,000 in equity versus nothing. Net difference: approximately $21,000 in favor of renting for a five-year horizon.

At seven years, the math flipped. Buying pulled ahead by roughly $8,000.

Marcus had always assumed buying was better. The calculator showed him it depended entirely on how long he stayed — and that at five years, the difference was smaller than he thought either way.

Step 5 — What he did with all of this

Marcus went back to his lender — not to accept the $420,000 ceiling, but with a counter-position.

He said he was looking in the $290,000–$310,000 range, was targeting a 13% down payment, and needed a back-end DTI under 43%. He asked what rate he'd qualify for at that loan size.

The conversation was different from his first call. He wasn't asking the lender to tell him what he could afford. He was telling the lender what he'd decided and asking them to confirm the rate.

He got 6.65% — 15 basis points lower than the initial quote, on a smaller loan. His monthly payment came in at $1,982 all-in including taxes and insurance.

He put in an offer at $298,000 the following month.

The framework, simplified

If you're trying to answer “how much house can I actually afford?”, the sequence Marcus used takes about an hour and four calculators:

First, run a mortgage payment calculation at a few different price points to see what principal and interest actually looks like at current rates. Then add property tax, insurance, and PMI to get the true monthly cost — the number lenders often leave out of their headline figure.

Second, run your DTI with that true housing cost plus your existing debts. If your back-end DTI clears 43%, recalibrate the purchase price until it doesn't.

Third, run the rent vs. buy comparison at your realistic time horizon — not the one where everything goes well, but the one you'd actually bet money on. The result might surprise you.

Fourth, if you already own and are refinancing rather than buying, run the refinance break-even to make sure a lower rate actually saves you money once closing costs are factored in.

The lender's job is to tell you the maximum they'll lend. Your job is to decide what you want to borrow. Those are different numbers — and only one of them starts with your budget.