A rate "lock" or "commitment" is a lender's promise to freeze a specific interest rate and a specific number of points for you for a certain period while your application is processed. This keeps you from getting through your entire application process and discovering at the end that your interest rate has risen higher.
While there can be a choice of rate lock periods (from 15 to 60 days), the longer spans are generally more expensive. You can get a longer period for your lock, but in making this choice, will most likely have a higher rate than you would with a shorter rate lock span of time
In addition to opting for a shorter rate lock period, there are other ways you can attain the best rate. A bigger down payment will result in a lower interest rate, since you're starting out with more equity. You could opt to pay points to improve your interest rate over the term of the loan, meaning you pay more initially. To many people, this makes financial sense..
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