How much you need for a down payment depends on the type of loan and how much the house costs, but the more you can put towards a down payment, the lower your monthly payment can be and the more you'll save on interest. Conventional loans typically require a down payment of at least 5% of a home's price. FHA loans require as little as 3.5%.
Along with your down payment, you'll have to pay closing costs, or fees associated with processing and securing your loan. These can vary depending on the price of the house and the type of mortgage, but estimate between 2% and 5% of the home's value.