When you are offered a "rate lock" from the lender, it means that you are guaranteed to keep a specific interest rate for a determined period for the application process. This keeps you from going through your whole application process and learning at the end that the interest rate has gone up.
Although there can be a choice of rate lock periods (from 15 to 60 days), the extended spans are usually more expensive. The lending institution will agree to freeze an interest rate and points for a longer period, say 60 days, but in exchange, the rate (and sometimes points) will be higher than that of a rate lock of a shorter period.
In addition to going with a shorter rate lock period, there are more ways you may be able to attain the lowest rate. The more the down payment, the smaller your interest rate will be, as you will have more equity from the beginning. You can pay points to bring down your interest rate over the loan term, meaning you pay more initially. For a lot of people, this makes sense and is a good deal..
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