 So look at the price of a typical home and ask how much of a down payment the household would have to pay so it could buy the home with its mortgage payments small enough to keep total monthly home payments within that 30% limit. Do the math and you can forget about the traditional 20% down payment. Now you'd need a 35% down payment if you're a median household buying a typical U.S. home. The calculations are by the Zillow Real Estate Company.