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 protects you from getting through your whole application process and finding out at the end that your interest rate has gone up.
Rate lock periods can vary in length, between fifteen to sixty days, with the longer spans generally costing more. You can get a longer period for your lock, but in choosing this option, will probably have a higher interest rate than you would with a shorter span of time
In addition to choosing the shorter rate lock period, there are other ways you can attain the best rate. A larger down payment will result in a lower interest rate, since you will have more equity at the start. You could opt to pay points to bring down your interest rate for the loan term, meaning you pay more up front. For many people, this makes financial sense..
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