A pre-approval can be done on the spot and have an automatic response back within minutes of the application through some lenders if their rate is the best. This works great for clients where credit, ratios, and down payment are very straight forward. Otherwise, it takes about 24 hours to have a lender look and send back the pre-approval certificate. Depending on the lender, most pre approval rates are held for 120 days, during this time.. Happy House Hunting!