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Mortgage Underwriting Engine

House Affordability

Quantify your buying power. Analyze your debt-to-income (DTI) ratios and determine your safe home-buying ceiling based on institutional lending standards.

Lending Market Assumptions

Pro Underwriting: Lenders use the **28/36 Rule**. Your mortgage shouldn't exceed 28% of your gross income, and total debt shouldn't exceed 36%.

Mortgage Underwriting Analytics

Defining Your
Home Buying Power

In the world of real estate, there is a difference between what a bank will lend you and what you can actually afford. While a lender might approve you for a massive loan, they don't account for your child's daycare, your travel plans, or your retirement goals. Our House Affordability Calculator uses the industry-standard 28/36 Rule to provide a realistic ceiling, ensuring your new home is a source of joy, not financial stress.

The 28/36 Rule

A core lending benchmark: Your housing costs (PITI) shouldn't exceed 28% of your gross income, and total debt (PITI + all other loans) shouldn't exceed 36%.

Back-End DTI

Your **Debt-to-Income** ratio is the most critical factor in mortgage approval. A back-end DTI over 43% is the absolute limit for most qualified mortgages.

Buying Capacity

By combining your down payment, interest rate, and income, we solve for the maximum "Sticker Price" you can offer on a home.

Front-End vs. Back-End Ratios

When a lender reviews your application, they look at two specific ratios:

  • Front-End Ratio: The percentage of your gross income that goes toward housing expenses (Principal, Interest, Taxes, Insurance, and HOA).
  • Back-End Ratio: The percentage of your gross income that goes toward all recurring debt, including car loans, student loans, and credit card minimums.

A borrower with no car payments can afford a significantly more expensive house than one with a $700/month truck payment, even if their salaries are identical.

The Hidden Costs of Purchase

Many buyers deplete their entire savings on the Down Payment, leaving them "Cash-Poor" the day they get the keys. Always budget for:

  • Closing Costs: Expect to pay 2-5% of the home price for appraisal, title insurance, and lender fees.
  • Immediate Repairs: Even a "Move-In Ready" home often needs $5,000 - $10,000 in immediate maintenance or upgrades.
  • Emergency Reserve: Most lenders want to see that you have at least 2-6 months of PITI payments in the bank after closing.

Why Interest Rates Matter So Much

Because home loans are amortized over 30 years, a small change in the interest rate has a massive impact on your Affordability. A 1% increase in the rate can reduce your buying power by roughly 10%. If you were approved for $400,000 at 6%, you might only be approved for $360,000 at 7%.

Home Buying Pro Tips:

  • • Pay Down Debt First: Reducing your car loan or student debt by $200/month could increase your mortgage approval by $30,000.
  • • Check Your Credit: A score of 740+ gets you the best rates. If you are at 680, wait 6 months and improve your score to save tens of thousands in interest.
  • • The HOA Trap: Homeowners Association fees are part of your DTI. A $500/month HOA fee effectively removes $70,000 of buying power from your mortgage.

The Quality of Life Buffer

Just because you are **Approved** for a $500k house doesn't mean you should buy it. Most financial planners recommend staying well below your maximum limit to ensure you can still afford vacations, hobbies, and retirement savings.

How to Use This Tool

Input your "Gross Annual Income" and the "Cash for Down Payment" you have available. Be honest about your "Existing Monthly Debt." Adjust the assumptions for "Interest Rate" and "Property Tax" based on your local market. The calculator will immediately solve for your Maximum Affordable Home Price and provide a Underwriting Analysis to show how your DTI ratios compare to industry standards.

How the calculation works

A common lending screen keeps the housing payment near 28% of gross monthly income and total debt near 36%.

Housing allowance = Gross monthly income × 0.28 Total debt allowance = Gross monthly income × 0.36

Lenders also look at credit, down payment, and the full PITI payment. These percents are a starting screen.

Worked example: $8,000 gross monthly income

  1. Housing at 28% = $2,240.
  2. All debt payments at 36% = $2,880.
  3. If other debts are $400, the room left for housing inside the 36% cap is $2,480, so the 28% cap of $2,240 is the tighter one.

28% housing allowance

Gross monthly income28% housing36% all debt
$5,000$1,400.00$1,800.00
$8,000$2,240.00$2,880.00
$12,000$3,360.00$4,320.00

Frequently asked questions

What housing payment is 28% of $8,000 a month?▼
$2,240. That figure is meant to include principal, interest, taxes, and insurance.
What is the 36% debt cap?▼
$2,880, including the housing payment and other monthly debts.
Which cap applies?▼
The lower of the 28% housing limit and whatever is left after other debts inside the 36% limit.