When you are offered a "rate lock" from a lender, it means that you are guaranteed to keep a certain interest rate for a certain number of days for your application process. This means your interest rate won't get higher during the application process.
Although there might be a choice of rate lock periods (from 15 to 60 days), the extended ones are generally more expensive. A lending institution will 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.
There are more ways to get a reduced rate, besides going with a shorter rate lock period. The larger the down payment, the better your rate will be, because you will be starting with more equity. You can pay points to lower your interest rate for the loan term, meaning you pay more up front. To many people, this makes sense and is a good deal..
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