How Much House Can You Afford?

Lesson 4.1

Total Monthly Payment: The Full PITI Picture

When someone asks "what will my mortgage payment be?", they usually mean the principal and interest payment — the number your lender quotes. But that's not your true monthly cost. The real number is your PITI payment: Principal, Interest, Taxes, and Insurance.

Breaking Down PITI

• Principal (P) — the portion of your payment that reduces your loan balance each month. Starts small, grows larger over time as the loan amortizes.
• Interest (I) — the cost of borrowing, calculated on your outstanding balance. Starts large, shrinks over time.
• Taxes (T) — property taxes, typically collected monthly into an escrow account and paid by the lender when they come due. Rates vary significantly by state and county.
• Insurance (I) — homeowners' insurance, also typically escrowed. If your down payment is below 20%, this also includes mortgage insurance (PMI or MIP).
• HOA dues — if the property is part of a homeowners association, monthly dues are an additional cost on top of PITI. Most first-time buyers won't encounter this — unless they're buying a condo, where HOA fees are common. It's more typical with higher-end homes and move-up purchases. If the home you're considering has an HOA, make sure you know the monthly amount before you decide what you can afford.

The PI portion of your payment is determined by your loan amount, interest rate, and term. The TI portion depends on where you're buying. This is why two buyers with the same loan amount can have very different monthly payments.

Why State Matters More Than Most Buyers Realize

Property tax rates vary enormously across the country. In Texas and New Jersey, effective property tax rates average over 2% of assessed value annually — on a $400,000 home, that's $8,000 per year or $667 per month just in taxes. In Hawaii or Alabama, the same home might carry property taxes of $150–$200 per month. That's a $400–$500 per month difference on the same purchase price.

Homeowners' insurance also varies by state — Florida, Louisiana, and other hurricane-prone states can carry insurance costs 2–4 times the national average.

Lesson 4.2

How Lenders Calculate What You Can Borrow

Lenders don't just look at income. They look at the relationship between your income and your debts — and between your income and your proposed housing payment. These two ratios are how lenders decide whether you qualify — and by how much.

The Two Qualification Ratios

Front-end ratio (housing ratio): Your proposed monthly PITI payment divided by your gross monthly income. For conventional loans, the front-end ratio is rarely the deciding factor in modern underwriting — automated systems focus primarily on the back-end ratio. For government loan programs (FHA, USDA), the front-end ratio still plays a role.

Back-end ratio (total debt ratio): Your proposed housing payment plus all other monthly debt obligations (car loans, student loans, minimum credit card payments, child support), divided by gross monthly income. This is the number that matters most. Most conventional lenders allow this up to 45%, with some allowing 50% for strong borrowers.

Example: $8,000 gross income × 45% = $3,600 total allowable debt. If you have $600/month in car payments and student loans, your maximum housing payment is $3,000.

What Counts as Income

Lenders count your gross income (before taxes), not your take-home pay. For W-2 employees, this is straightforward. For self-employed borrowers, income is typically the average of the past two years of net business income from tax returns — which is often lower than what you actually earn.

Lenders can also count overtime, bonuses, commission, rental income, alimony, and child support — but typically require a two-year history of these income sources to document they're stable and likely to continue.

What Counts as Debt

Lenders count all installment loans (car, student, personal), minimum monthly credit card payments, child support and alimony obligations, and any other recurring debt obligations that appear on your credit report. They do not count utilities, cell phones, subscriptions, or other living expenses.

Lesson 4.3

Pre-Qualification vs. Pre-Approval

These two terms are often used interchangeably by buyers, but they're very different — and mixing them up can cost you a deal in a competitive market.

Pre-Qualification

Pre-qualification is an informal estimate based on information you self-report to the lender. You tell them your income, your debts, and your down payment. They run no credit check, verify none of it, and give you a ballpark of what you might qualify for. It typically takes 10–15 minutes.

Pre-qualification is useful for early planning — figuring out what price range to explore. It is not taken seriously by sellers or listing agents in most markets, because it carries no verification behind it.

Pre-Approval

Pre-approval is a genuine underwriting review. The lender verifies your income with W-2s and pay stubs, verifies your assets with bank statements, and pulls a full tri-merge credit report. They run your application through automated underwriting software (Fannie Mae's Desktop Underwriter or Freddie Mac's Loan Product Advisor) and issue a conditional approval based on verified data.

A pre-approval letter from a reputable lender tells a seller that a real lender has looked at your actual financials and confirmed you qualify — subject to an appraisal and property review. This carries real weight in an offer.

Full Underwriting Approval (Credit Approval)

Some lenders offer what's called a fully underwritten credit approval — where a human underwriter reviews the file before you even find a house. The only remaining condition is a satisfactory appraisal on the specific property. In competitive markets, this is the strongest possible position for a buyer and can sometimes be leveraged similarly to a cash offer.

What You'll Need for Pre-Approval

• Last two years of W-2s (or federal tax returns if self-employed)
• Most recent 30 days of pay stubs
• Last two to three months of bank and investment account statements
• Valid government-issued ID
• Authorization to pull your credit
• Documentation of any additional income (rental, alimony, Social Security)

Lesson 4.4

The Income Needed Calculation

Most affordability discussions start from income and work forward to home price. But there's a useful exercise in working backward: starting from a home price you want to buy, and calculating the income needed to qualify for it. This tells you directly whether you're in range — or how far off you are.

How the Calculation Works

The income needed is determined by back-engineering the qualification ratios. Take the estimated full monthly PITI payment for your target home price and down payment, then divide by the maximum back-end ratio allowed for your loan type.

Example: You want to buy a $400,000 home in Texas with a 5% down payment ($20,000 down, $380,000 loan) on a 30-year conventional loan at 7%. The estimated full PITI in Texas (with its higher property taxes) might be approximately $3,400/month. If you carry $500/month in other debt, your total monthly obligations are $3,900. At a 45% back-end ratio, the required gross income is $3,900 ÷ 0.45 = $8,667/month, or roughly $104,000/year.

The same home price in a lower-tax state requires less income to qualify because the PITI is lower.

The Impact of Down Payment on Income Requirements

A larger down payment lowers the loan amount, which lowers the P&I payment, which lowers the PITI total, which lowers the income required. It also eliminates or reduces PMI, lowering PITI further. This is one of the most direct ways a down payment affects what you can qualify for — not just what you owe.

Self-Employed Borrowers: The Write-Off Trap

Self-employed borrowers face a qualification challenge that W-2 employees don't. Lenders don't qualify you on your gross business revenue — they qualify you on your net income after business expenses, as reported on your federal tax returns. That's the number that shows up on your Schedule C or K-1, and that's what the lender uses.

Here's the conflict: most self-employed people work hard to minimize their taxable income by writing off as many legitimate business expenses as possible. That's smart tax strategy. But it's the opposite of what you need when you're trying to qualify for a mortgage. The lower your reported net income, the less home you can qualify for — even if your actual cash flow is healthy.

The fix requires planning well ahead of your purchase. Lenders want to see at least two years of stable, consistent qualifying income — and the most recent year alone usually isn't enough. If you show strong income in year two but weak income in year one, underwriters will often average the two, or use the lower year. Either way, one good year doesn't rescue two years of aggressive write-offs.

Think of it as an investment. If you're planning to buy a home in the next two years, talk to your accountant now about what your qualifying income looks like on paper. Paying a bit more in taxes for two years in order to qualify for the home you want is often the better financial decision overall — especially when you factor in equity, appreciation, and the tax benefits of homeownership itself.

Co-Borrowers

Adding a co-borrower (a spouse, partner, or parent) means their income can be included in the qualification calculation. Their debts are also included, however, so the net benefit depends on their income-to-debt ratio. A co-borrower with significant debt but modest income may not help — or could hurt the qualification.

Lesson 4.5

Rent vs. Buy: A Financially Honest Comparison

"Renting is throwing money away." You've heard this. It's not quite right — and believing it has pushed plenty of people into buying before they were financially ready, or buying in markets where the math didn't work in their favor.

The rent vs. buy decision is a real financial calculation, and it deserves a real analysis.

The True Cost of Buying

Buying a home carries costs that renting doesn't:

• Transaction costs: Closing costs on purchase (2–5% of loan amount). Selling costs eventually (8–10% of sale price including commissions). Together, these can amount to 12–15% of the home's value over the ownership period.
• Opportunity cost of the down payment: Money tied up in a down payment could be invested elsewhere. A $40,000 down payment invested in a broad market index fund over 10 years might grow to $80,000+ depending on market returns.
• Maintenance and repairs: Renters don't pay these. Owners should budget 1–2% of home value per year.
• Property taxes and insurance: Paid by the owner; typically included in a renter's rent payment (indirectly) but not as a separate line item.

The True Cost of Renting

Renting has its own costs beyond the monthly payment:

• Rent increases over time — you have limited control over your housing cost long-term
• No equity building — every dollar in rent leaves your balance sheet
• No forced savings — renters must be disciplined about investing the difference
• No leverage benefit — homeowners benefit from appreciation on the full home value (not just their down payment)

The Break-Even Horizon

The central question in rent vs. buy analysis is: how long do you need to stay for buying to be the better financial decision? This is called the break-even horizon. In most markets, it falls between 3 and 7 years. In very high-cost markets like San Francisco or New York, it can stretch to 10+ years.

If you're likely to relocate within 3–4 years, renting is often the financially smarter choice — the transaction costs of buying and selling within a short window can exceed any appreciation gains. If you're settling in for a decade or more, buying generally wins, especially if your alternative is renting the equivalent home.