How Much House Payment Can You Actually Afford? A San Antonio Buyer's Budget Worksheet

The short answer: your budget number and the lender's ceiling are two separate questions.

A lender qualifies you against a maximum debt-to-income ratio that changes by loan program, not a single national rule. Conventional loans run through Desktop Underwriter can reach 50% DTI, FHA benchmarks sit at 31% front-end and 43% back-end, USDA benchmarks sit at 29% and 41%, and VA does not use a hard DTI ceiling at all; it qualifies on residual income first. None of those ceilings is a personal budget. The number you should actually spend to is the smaller of what underwriting will approve and what your own housing budget, including Bexar County-specific costs beyond principal and interest, can carry.

This article builds both numbers side by side. For the offer and closing sequence that follows preapproval, see the down payment and cash-to-close guide and when to talk to a lender before house hunting.

The DTI ceiling depends on the loan program, not a blended national rule.

As reviewed on September 11, 2026, the Fannie Mae Selling Guide section on debt-to-income ratios states that for loan casefiles underwritten through Desktop Underwriter (DU), the maximum allowable DTI ratio is 50%. Manually underwritten conventional loans are held to a lower base of 36% of stable monthly income, which can be exceeded up to 45% if the borrower meets the credit score and reserve requirements in Fannie Mae's Eligibility Matrix.

The HUD Handbook 4000.1 benchmark for FHA loans is a housing-expense ratio of 31% and a total debt ratio of 43% of gross monthly income. Exceeding either does not automatically disqualify a borrower, but it requires the lender to document compensating factors such as cash reserves, minimal payment shock versus current housing costs, or strong residual income. USDA's Single Family Housing Guaranteed Loan Program handbook sets its benchmark PITI ratio at 29% and total debt ratio at 41%, again subject to compensating factors.

Front-end and back-end ratios, worked through a San Antonio-area price point.

The front-end (housing) ratio only counts your proposed mortgage payment, including principal, interest, taxes, insurance, and any HOA or MUD/PID assessment, divided by gross monthly income. The back-end (total debt) ratio adds every other recurring debt: car payments, student loans, credit card minimums, and similar obligations.

Consider a household with $7,500 in gross monthly income evaluating a $340,000 home in a Bexar County subdivision with a homeowners association. A lender's estimate of principal, interest, property taxes, homeowners insurance, and HOA dues might total roughly $2,700 a month. That is a 36% front-end ratio ($2,700 ÷ $7,500). If the household also carries a $450 car payment and $150 in minimum credit card payments, total monthly debt service is $3,300, a 44% back-end ratio ($3,300 ÷ $7,500). Under FHA's 31%/43% benchmark, the front-end ratio already exceeds guideline and the back-end ratio is close to the ceiling, which would likely require documented compensating factors. Under a DU-underwritten conventional loan with a 50% ceiling, the same household would likely qualify without extra documentation. The loan program you use changes the answer to the exact same numbers.

VA buyers qualify on a different standard: residual income, not a DTI cap.

VA Pamphlet 26-7, Chapter 4 instructs underwriters to weigh a borrower's residual income more heavily than DTI. This matters for San Antonio because of the region's large JBSA-adjacent military and veteran buyer population, and it is the exact path the competing national budgeting tools in this market generally omit.

Residual income is what is left over each month after the underwriter subtracts the full proposed housing payment (principal, interest, taxes, insurance, and any HOA or MUD/PID assessment), other recurring debts, estimated federal and state taxes, and an allowance for maintenance and utilities based on the home's square footage. The VA divides the country into four regions, and the minimum required residual income scales up with family size within each region; loans under $80,000 and loans at or above $80,000 use separate tables. A DTI ratio above 41% does not disqualify a VA borrower outright, but it raises the required residual income by 20% above the standard chart minimum for that region and family size. Strong residual income can offset a DTI ratio that would be disqualifying under a program that uses a hard ceiling.

Practically, this means a VA-eligible buyer whose DTI looks high on a conventional or FHA scale may still qualify comfortably once residual income is calculated correctly, and a buyer with a "passing" DTI but thin residual income could still be asked for compensating factors. The two measurements answer different questions, and a VA file is underwritten on both.

Add the Bexar County cost lines a national calculator will not know.

Two households with identical incomes and identical loan amounts can have different qualifying payments once county-specific costs are added. A budget that only accounts for principal and interest is not the number underwriting will use.

Property tax rate

As reviewed on September 11, 2026, the Bexar County Tax Assessor-Collector's official 2025 tax rate notice lists the county's own rate at $0.276331 per $100 of assessed property value. That is only the county's line item. The total tax bill a lender escrows also includes the applicable city, school district, and any other overlapping taxing jurisdiction, so the combined effective rate on a specific property will be higher than the county rate alone. Confirm the full combined rate for the specific parcel using the Bexar County Tax Assessor-Collector's property tax search before finalizing a budget.

Homeowners insurance

Homeowners insurance premiums vary by insurer, coverage level, construction, and claims history, and this article does not publish a single average figure because none would be accurate for a specific property. Get a written quote for the specific home under consideration and add the actual monthly premium, not an estimate, to the front-end ratio calculation before treating a preapproval number as final.

MUD, PID, and HOA fees common in newer San Antonio-area subdivisions

Municipal Utility Districts (MUDs) and Public Improvement Districts (PIDs) are common in newer San Antonio-area subdivisions and can add a separate tax or annual assessment on top of standard property taxes. Texas Water Code Chapter 49 requires a seller to give a buyer written notice of a MUD's tax rate, bonded indebtedness, and fees before the buyer signs a contract, or as an addendum at the time the contract is negotiated; if that notice is not timely provided, the buyer can terminate the contract. Texas law imposes a comparable notice requirement for PID assessments. Ask for the MUD or PID notice on any new-construction or newer-subdivision property and add the disclosed annual amount, divided by twelve, into the front-end ratio alongside any HOA dues.

A worked walkthrough you can run with your own numbers.

No login or contact information is required to work through this. Use your own figures in place of the example above:

1. Add your gross monthly income from all qualifying sources.
2. Estimate principal and interest for the loan amount you are considering.
3. Add the actual, parcel-specific property tax estimate (county rate plus city, school, and any other jurisdiction).
4. Add a written homeowners insurance quote for the specific property, not a placeholder figure.
5. Add any HOA dues and, if applicable, the disclosed MUD or PID assessment divided by twelve.
6. Divide that total housing payment by your gross monthly income. That is your front-end ratio.
7. Add your other recurring monthly debts to the housing payment, then divide by gross monthly income again. That is your back-end ratio.
8. Compare both ratios to the benchmark for the loan program you expect to use, or, for a VA loan, ask your lender to run the residual income calculation instead.

If the result is below your program's benchmark but still higher than you want to actually spend every month, use the lower number. A lender's ceiling describes what the file can support; it does not describe what fits your life.

Avoid these common budgeting mistakes.

1. Using one DTI rule for every loan type. The benchmark changes by program, and VA does not use a hard ceiling at all.
2. Budgeting from the county tax rate alone. The county's own rate is one line among several that make up a property's total tax bill.
3. Skipping the MUD or PID question on a newer subdivision. Ask for the required notice before you are under contract, not after.
4. Treating the lender's maximum as the target. Set your own ceiling using your full budget, not the largest number underwriting will approve.

This worksheet is general mortgage education, not a substitute for a full application review. Confirm the exact ratios, residual income requirement, and cost estimates that apply to your file and property with a lender before finalizing a search budget.

Official sources used for this article

This article cites government and agency sources for the ratios and figures it summarizes. Source pages can change. Review the linked material directly and confirm current requirements with the appropriate professional.

1. Fannie Mae Selling Guide B3-6-02: Debt-to-Income RatiosStates the 50% DU maximum and the 36%/45% manual underwriting ratios. Accessed September 11, 2026.
2. HUD Handbook 4000.1: FHA Single Family Housing Policy HandbookSets the 31%/43% FHA benchmark qualifying ratios and compensating-factor extensions. Accessed September 11, 2026.
3. VA Pamphlet 26-7, Chapter 4: Credit UnderwritingDescribes the VA residual income standard, the four-region table, and the 41% DTI/20% residual-income flag. Accessed September 11, 2026.
4. USDA HB-1-3555, Chapter 11: Ratio AnalysisSets the 29%/41% USDA Guaranteed Loan benchmark ratios. Accessed September 11, 2026.
5. Bexar County: 2025 Official Tax Rates & ExemptionsStates the county's 2025 rate of $0.276331 per $100 of assessed value. Accessed September 11, 2026.
6. Texas Water Code, Chapter 49Requires seller notice of a MUD's tax rate, bonded debt, and fees before or at contract. Accessed September 11, 2026.