A rate "lock" or "commitment" is a promise from the lender to set a certain interest rate and a certain number of points for you for a specified period while your application is processed. This keeps you from working through your entire application process and discovering at the end that your interest rate has gotten higher.
Rate lock periods can vary in length, anywhere from 15 to 60 days, with the longer ones typically costing more. You can get a longer period for your lock, but in doing so, will likely have a higher interest rate than you would with a shorter rate lock period
There are other ways to get a lower rate, besides going with a shorter rate lock period. The bigger down payment you can make, the lower your interest rate will be, since you will be entering the loan with more equity. You can pay points to lower your rate over the life of the loan, meaning you pay more initially. For many people, this makes sense and is a good deal..
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