A rate "lock" or "commitment" is a lender's promise to lock in a certain interest rate and a certain number of points for you for a specified period during your application process. This saves you from getting through your whole application process and learning at the end that the interest rate has gotten higher.
Although there might be a choice of rate lock periods (from 15 to 60 days), the extended spans are generally more expensive. You can get a longer period for your lock, but in choosing this option, will likely have a higher rate than you would with a shorter rate lock span of time
There are more ways to get a good rate, in addition to opting for a shorter rate lock period. The larger the down payment, the lower your rate will be, because you will have more equity from the beginning. You can pay points to lower your interest rate for the life of the loan, meaning you pay more initially. For a lot of people, this is a good option..
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