The flights take off pretty frequently, so you'll probably be able to hear them during your visit to the property and judge for yourself. We were concerned about it before we bought, and especially the minute we signed our loan!
Truthfully we don't notice it anymore unless all the windows are open right during a really important, quiet part of dialogue when we're watching a DVD. The airport paid for soundproofing for the neighborhood, so with windows closed it's not an issue at all, and with windows open we noticed it for a few hours the first day and haven't really thought about it since.
The flights on the runway nearest to us stop at night, so that helps as well.