The old fashioned answer is 20%, but many people don't put down this much. Conventional mortgages allow down payments as low as 3%, while FHA borrowers will need at least 3.5%. If you qualify for a USDA or VA mortgage, you won't need to make a down payment. Don't forget to factor in closing costs. These can cost between 3% and 6% of the loan amount, and you'll owe them along with your down payment at closing.