An interest rate lock is always a good idea in any market. But it becomes a better idea when it's crucial to lock in an interest rate and other loan costs at a level you can afford. A changing market -- especially when the change is for the worst -- is one of those crucial times. During the first half of 2008, nearly a full percentage point separated the high of 6.45 percent in recent weeks and the low of 5.48 percent in January, according to Freddie Mac. Get off the interest rate elevator ride with an interest rate (0 comments)