Second Home Affordability Calculator

Background.

Use Second Home Affordability Calculator when you need to translate a lender DTI ceiling into principal-and-interest capacity for a second home. The residual DTI method subtracts existing debts, primary housing and the second home's non-mortgage costs from allowable monthly obligations. Here the arithmetic follows “maximum second-home principal and interest = max(gross income × lender DTI − existing debts − primary housing − second-home taxes/insurance/HOA, 0),” rather than silently mixing alternatives.

The editable entries are gross monthly income, lender maximum total dti, existing monthly debt obligations, primary-home monthly payment, second-home monthly taxes, insurance and hoa. Use values from the document or measurement that governs this second home affordability question; the defaults are only the worked fixture below. The most consequential input mistake would be to ignore that reserves, rental income, occupancy classification, credit overlays and interest-rate qualification are not determined.

Fannie Mae Selling Guide B3-6-02, Debt-to-Income Ratios documents the convention or governing rule used here. The second home affordability output is a transparent scenario under those facts: it does not manufacture an unentered market price, professional determination, carrier quote, legal eligibility finding or locally adopted code value.

What is second home affordability calculator?

Second Home Affordability is the relationship behind this decision: the residual DTI method subtracts existing debts, primary housing and the second home's non-mortgage costs from allowable monthly obligations. On this page it means maximum second-home principal and interest = max(gross income × lender DTI − existing debts − primary housing − second-home taxes/insurance/HOA, 0). Reserves, rental income, occupancy classification, credit overlays and interest-rate qualification are not determined; that is the line between the reported quantity and a broader mortgage analysis.

How to use this calculator.

1. 01Confirm that “maximum second-home principal and interest = max(gross income × lender DTI − existing debts − primary housing − second-home taxes/insurance/HOA, 0)” matches the second home affordability convention you need.
2. 02Replace the fixture values for gross monthly income, lender maximum total dti, existing monthly debt obligations, primary-home monthly payment, second-home monthly taxes, insurance and hoa with dated values from the governing record.
3. 03Keep all currencies, measurement units and time periods on the same basis before calculating.
4. 04Read maximum second-home principal and interest together with this boundary: Reserves, rental income, occupancy classification, credit overlays and interest-rate qualification are not determined.

The formula.

The calculation uses maximum second-home principal and interest = max(gross income × lender DTI − existing debts − primary housing − second-home taxes/insurance/HOA, 0). In this second home affordability model, the entered terms are gross monthly income, lender maximum total dti, existing monthly debt obligations, primary-home monthly payment, second-home monthly taxes, insurance and hoa. The residual DTI method subtracts existing debts, primary housing and the second home's non-mortgage costs from allowable monthly obligations, which is why the relationship is presented under this name rather than as a universal alternative. Reserves, rental income, occupancy classification, credit overlays and interest-rate qualification are not determined. Calculations keep full decimal precision through the relationship and round only the returned display values.

A worked example.

Frequently asked questions.

References& sources.

1. [1]Fannie Mae Selling Guide B3-6-02, Debt-to-Income Ratios. Retrieved 2026-08-07. access: open unless marked otherwise.
2. [2]Fannie Mae. Single family selling guide. Retrieved 2026-08-07. independence: primary; access: open.
3. [3]U.S. Internal Revenue Service. Publication 936, Home Mortgage Interest Deduction. Retrieved 2026-08-07. independence: primary; access: open.