An independent calculator for the keep-and-buy decision.

Who runs this

keepitrentit.com is published by Red Goggles LLC, an independent operator of free web calculators and reference tools. We are not a lender, a mortgage broker, a real-estate agent, or affiliated with Fannie Mae, Freddie Mac, or any financial institution. We don't originate loans, we don't collect leads, and we don't take your information — the calculator runs on your device and nothing you type is sent to us.

Why this site exists

Move-up buyers keep hitting the same wall: they want to keep the current home — often for a low locked-in rate — and rent it out rather than sell, but both mortgages at once usually push their debt-to-income ratio past the lender's ceiling. Conventional underwriting has a specific escape hatch for exactly this — the departing-residence rental offset — yet the generic "DTI calculators" that rank don't model it, and the broker blog posts that explain it don't give you a calculator. This tool sits in that gap: it runs the actual offset math so you can see the before-and-after swing before you call a lender.

How it's calculated

The estimate applies the conventional departing-residence rule, in the open:

• 75% of projected gross rent. The lender counts 75% of the projected gross monthly rent; the other 25% is a standard vacancy-and-maintenance allowance.
• Netted against the full old PITIA. That 75% figure is netted against the entire existing payment on the departing home — Principal, Interest, Taxes, Insurance, and Association (HOA) dues. A surplus is added to qualifying income; a shortfall is added to monthly debts. The offset nets against the old payment; it does not simply make it disappear.
• Re-run against the back-end ceiling. Back-end DTI is recalculated with the offset applied and compared to a typical 45–50% ceiling. The real cap is driven by the automated-underwriting (DU/LPA) decision and lender overlays, so we present the ceiling as a selectable range, never as a guarantee.

The full method is spelled out on the calculator page under How it works and The 75% factor, step by step. The 75% factor, the net-rent-vs-PITIA treatment, and the PITIA definition follow the conventional departing-residence rule in the Fannie Mae Selling Guide (B3-3.8-01, Rental Income); the Freddie Mac Seller/Servicer Guide has an equivalent.

How we stay accurate and current

This is a six-figure financial decision, so precision matters. We model the mainstream conventional (Fannie/Freddie-style) departing-residence offset only — FHA, VA, USDA, jumbo, and non-QM programs apply different rental and occupancy rules, and we say so rather than letting conventional logic leak across loan types. We're careful with terminology: this is a departing residence being converted to a rental, not a "second home" (a true second home is owner-occupied and can't use rental income at all). Underwriting guidelines change, so every page carries a "Last updated" date and a standing note to verify the current Selling Guide and confirm your specific automated-underwriting findings with a licensed loan officer.

How the site is funded

keepitrentit.com is free and supported by display advertising. Advertising is kept calm and never mixes with your inputs — see our privacy page for exactly what is and isn't collected.

Questions or corrections? We take accuracy seriously on a decision this consequential — reach us on the contact page.