The math seems simple: the higher your down payment, the lower your mortgage loan amount will be, and the less you will pay in interest over time. The size of your down payment might also impact your loan eligibility. In most cases, you will need a minimum of at least 3 percent, and many loan types will require 5 percent, or more, down. Most lenders will also require that you pay Private Mortgage Insurance (PMI) if you put down less than 20 percent until your loan-to-value reaches 80 percent. It is a good idea to give yourself a cash cushion so that you will have money available for the unexpected when you purchase a home. Work with your lender to determine how to 'right-size' your down payment.