There are several types of mortgage loans you can get to buy a house, and there are various down payment amounts with each type. Simply put, the more money you put down, the lower your mortgage payment. And the larger the down payment, the lower your interest rate will be.
Down payments range from 3% - 20%. You may see ads that say you can buy a house for no money down. In the early 2000's, it was fairly easy to find 0% down loans. With changes in the economy, the increase in the number of foreclosures, and the sub-prime lending crisis, these no cost loans are few and far between, unless you are a military veteran with good credit.
These changes have also made it more difficult for anyone with poor credit to qualify for a loan to buy a house. With less than stellar credit, expect to pay higher interest rates. And if you put anything less than 20% down, you will be required to buy Private Mortgage Insurance that can amount to quite a bit of money.