Fha Loan Rental Property Using Rental Income to Qualify. An investment property can help you gain fha financing when you use net rental income to qualify. The lender multiplies the gross rent you charge by a vacancy factor — usually 25 percent — to account for potential vacancy and repairs. It then subtracts the total monthly housing payment, including principal,How Much Down Payment For Fha Under the new FHA mortgage insurance rules, when you use a 30-year fixed rate FHA mortgage and make a down payment of 3.5 percent, your FHA mortgage insurance premium (MIP) is 0.85% annually.