A rate "lock" or "commitment" is a promise from the lender to hold a specific interest rate and a particular number of points for you for a certain period while your application is processed. This means your interest rate will not get higher during the application process.
Rate lock periods can vary in length, between fifteen to sixty days, with the longer spans usually costing more. You can get a longer period for your lock, but in making this choice, will probably have a higher rate than you would with a shorter span of time
There are more ways to get a lower rate, besides choosing a shorter rate lock period. The bigger down payment you can pay, the better the interest rate will be, because you will be entering the loan with more equity. You may choose to pay points to improve your interest rate over the life of the loan, meaning you pay more up front. One strategy that is a good option for some is to pay points to reduce the rate over the life of the loan. You'll pay more initially, but you'll save money, especially if you don't refinance early.
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