When you are offered a "rate lock" from a lender, it means that you are guaranteed to get a specific interest rate for a certain number of days while you work on the application process. This ensures that your interest rate can't rise during the application process.
Although there may be a choice of rate lock periods (from 15 to 60 days), the extended spans are generally more expensive. A lender can agree to freeze an interest rate and points for a longer period, like 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 going with a shorter rate lock period, there are other ways you can score the lowest rate. The more the down payment, the lower your interest rate will be, since you will have more equity from the start. You may choose to pay points to bring down your interest rate over the life of the loan, meaning you pay more up front. One strategy that is a good option for many people is to pay points to bring the rate down over the term of the loan. You are paying more up front, but you will save money in the long run.
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