A rate "lock" or "commitment" is a lender's promise to set a particular interest rate and a particular number of points for you for a certain period of time while your application is processed. This keeps you from getting through your whole application process and discovering at the end that your interest rate has risen higher.
While there are various lengths of rate lock periods (from 15 to 60 days), the extended ones are typically more expensive. You can get a longer period for your lock, but in doing so, will most likely have a higher rate than you would have with a shorter period
In addition to going with the shorter lock period, there are several ways you may be able to get the best rate. The more the down payment, the lower the interest rate will be, as you will have more equity from the beginning. You can pay points to lower your interest rate over the life of the loan, meaning you pay more initially. To a lot of people, this makes financial sense..
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