When you are offered a "rate lock" from a lender, it means that you are guaranteed to get a set interest rate for a determined period for your application process. This means your interest rate can't rise while you are working through the application process.
Although there are several lengths of rate lock periods (from 15 to 60 days), the longer ones are usually more expensive. A lender will agree to hold an interest rate and points for a longer period, such as sixty days, but in exchange, the rate (and sometimes points) will be more than that of a rate lock of a shorter period.
There are other ways to get a reduced rate, in addition to opting for a shorter rate lock period. A bigger down payment will get you a lower interest rate, since you're starting out with a good deal of equity. You might choose to pay points to lower your rate for the loan term, meaning you pay more up front. One strategy that is a good option for some is to pay points to bring the rate down over the life of the loan. You pay more up front, but you'll come out ahead in the end.
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