A rate "lock" or "commitment" is a promise from the lender to hold a specific interest rate and a particular number of points for you for a specified period while your application is processed. This prevents you from working 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, anywhere from fifteen to sixty days, with the longer spans generally costing more. A lending institution can agree to lock in an interest rate and points for a longer period, such as sixty days, but in exchange, the rate (and sometimes points) will be higher than that of a rate lock of fewer days.
In addition to choosing a shorter lock period, there are more ways you can score the best rate. A larger down payment will get you a better interest rate, because you'll have more equity at the start. You could choose to pay points to lower your interest rate for the term of the loan, meaning you pay more up front. For many people, this makes sense and is a good deal..
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