Paying cash for a house is the least expensive way, by far. With cash, you don’t have to pay interest or a large chunk of your closing costs, and you could end up with an even better deal on the purchase. That said, even a physician usually cannot do that with their first house. The next cheapest way to buy a house is to put 20% down on a 15-year mortgage and then pay that off over 5-10 years.