A rate "lock" or "commitment" is a promise from the lender to freeze a specific interest rate and a specific number of points for you for a specified period during your application process. This protects you from getting through your entire application process and finding out at the end that the interest rate has risen higher.
While there may be a choice of rate lock periods (from 15 to 60 days), the extended spans are typically more expensive. You can get a longer period for your lock, but in choosing this option, will likely have a higher interest rate than you would have with a shorter span of time
In addition to going with the shorter rate lock period, there are more ways you are able to score the best rate. A bigger down payment will result in a better interest rate, since you'll be starting out with a good deal of equity. You can pay points to lower your interest rate for the loan term, meaning you pay more initially. For a lot of people, this makes financial sense..
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