Cellar Start-Up - Temperatures, storage methods, etc.

I am debating whether or not to convert my closet to cellar/storage space for brews. I live in NC, so the winters are cold and the summers are hot. I am trying to decide what is the best to store beer. Should I just purchase a fridge off of Craigslist, and go that route? I am on a limited budget, and I am also trying to figure out what temperature range is acceptable to store beer at. I know most websites say 50-55 degrees F, but does it really make a difference if it is closer to 60-65?