Two FHA rules decide this scenario: the 100-mile rule on your departing residence and the self-sufficiency test on the fourplex. Both affect how much you qualify for and how much cash you need. - The 100-mile rule. To count rental income from the home you are vacating, FHA requires that you be relocating more than 100 miles from it. And if that home has no rental history, the lender also needs a market-rent appraisal plus documentation that you have at least 25% equity in the property you are leaving. If the fourplex is within 100 miles of your current home, plan your down payment and debt-to-income around not using that rental income. - The self-sufficiency test. On 3-4 unit FHA purchases (1-2 unit properties are exempt), the appraiser establishes market rent for all the units, and 75% of that total has to equal or exceed the full monthly payment: principal, interest, taxes, insurance, mortgage insurance, and any HOA dues. The 25% haircut covers vacancy and maintenance. Some markets clear the test easily and others almost never do, so whether a given Alaska fourplex passes depends on local rents versus prices, property by property. Keep-or-sell on your current home comes down to those two constraints plus your available cash. FHA updates these guidelines, so confirm the current versions. Running the real numbers on a scenario like this is exactly what the free Roadmap conversation is for.