When you're promised a "rate lock" from your lender, it means that you are guaranteed to keep a certain interest rate for a determined period for your application process. This saves you from getting through your whole application process and discovering at the end that the interest rate has risen higher.
Although there are various lengths of rate lock periods (from 15 to 60 days), the extended ones are generally more expensive. The lender will agree to lock in 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 a shorter period.
In addition to choosing a shorter lock period, there are several ways you can score the lowest rate. A bigger down payment will give you a better interest rate, because you will have more equity from the beginning. You could opt to pay points to bring down your interest rate for the life of the loan, meaning you pay more initially. To many people, this makes sense and is a good deal..
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