The lump sum in cash that you can afford to pay at the time of purchase. Traditionally, down payments are 20% of the purchase price, so if you are buying a home for $500,000, your typical down payment would be $100,000. It is possible to put less than 20% down, but mortgage insurnace would then be required. No-down-payment loans exist for veterans and others, and there are also down payment assistance programs for first-time buyers.