A lock-in agreement secures a loan at a set interest rate prior to closing on the loan. This assures that the loan rate will remain set for a short period of time, usually 30 to 90 days. The opportunity to lock in a particular loan interest rate can be a great advantage to the buyer, especially when rates are increasing. Loan rates also fluctuate; if you lock in rates and then the rate goes down before closing, you will lose the advantage. Timing is important when you wish to lock in a loan. With real estate, it is possible that your lock-in time period could expire prior to the time you locate a home to purchase. For that reason, many borrowers do not seek loan approval or lock in until they find a home to buy. To lock in a loan rate, you pay a fee; longer terms cost more, so many borrowers prefer to wait to seek financing until they have found a home to buy.