A rate "lock" or "commitment" is a lender's promise to freeze a certain interest rate and a particular number of points for you for a specified period during your application process. This means your interest rate can't rise while you are going through the application process.
While there can be a choice of rate lock periods (from 15 to 60 days), the longer spans are usually more expensive. A lender may agree to hold an interest rate and points for a longer period, say 60 days, but in exchange, the rate (and sometimes points) will be more than that of a rate lock of fewer days.
There are more ways to get a lower rate, besides choosing a shorter rate lock period. The larger down payment you can pay, the smaller your rate will be, as you will have more equity from the start. You can pay points to improve your rate for the loan term, meaning you pay more initially. For many people, this makes sense and is a good deal..
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