A rate "lock" or "commitment" is a promise from the lender to lock in a particular interest rate and a certain number of points for you for a specified period during your application process. This ensures that your interest rate won't grow while you are working through the application process.
Rate lock periods can vary in length, between fifteen to sixty days, with the longer ones generally costing more. You can get a longer period for your lock, but in doing so, will probably have a higher rate than you would with a shorter rate lock period
There are other ways to get a good rate, in addition to choosing a shorter rate lock period. The larger the down payment, the lower the rate will be, because you will have more equity from the start. You might opt to pay points to improve your rate for the loan term, meaning you pay more initially. One strategy that is a good option for many people is to pay points to reduce the rate over the term of the loan. You will pay more initially, but you'll come out ahead in the end.
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