Start shopping for a mortgage when you're 'under contract' to buy a house. Under contract means you made an offer on the property, and the seller accepted it. To shop for a mortgage, research and compare offers from a few lenders to find the best mortgage loan for your needs. Here are some steps to follow when shopping for a mortgage: Find a reliable mortgage lender. Start with the lender that did your mortgage pre-approval letter.  Ask for an official Loan Estimate. Ask a few mortgage lenders for a Loan Estimate to shop for a mortgage. Review it carefully and compare it with other offers from different lenders to ensure you're getting the best deal possible. Lock the interest rate. Mortgage rates frequently fluctuate, so getting Loan Estimates on the same day is a good idea. Then, once you've found a lender and mortgage product you're comfortable with, lock in your interest rate to protect against sudden increases before closing on your new home.