Don't refinish the floor. If you have hardwood and it isn't in perfect shape, don't spend your money having the floors refinished.
Home buyers love hardwood, and it's always seen as an upgrade even if it's imperfect. Sometimes a good cleaning and some touch-ups with wood stain are all you need to revive your floor.
If your floor really needs more than that, consider a low-cost alternative to refinishing: Apply a fresh topcoat of nonyellowing polyurethane, found in the flooring section of a home improvement store.
Be sure to very lightly sand the floors with a pole sander and fine-grit sandpaper. No heavy sanding is necessary here. You are just looking to knock down the gloss so that the new coat of poly will stick. I've done this myself with 60-year-old hardwoods and couldn't believe how great the result was.