A rate "lock" or "commitment" is a promise from the lender to freeze a specific interest rate and a certain number of points for you for a specified period of time during your application process. This prevents you from working through your entire application process and learning at the end that the interest rate has risen higher.
Although there are several lengths of rate lock periods (from 15 to 60 days), the extended ones are usually more expensive. You can get a longer period for your lock, but in doing so, will likely have a higher interest rate than you would with a shorter span of time
There are more ways to get a better rate, besides agreeing to a shorter rate lock period. The bigger the down payment, the lower your interest rate will be, because you will be starting with more equity. You can pay points to lower your rate for the loan term, meaning you pay more up front. To many people, this is a good option..
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