To the OP. Search like crazy for something in your side. If your not sure head to a LBS to sit on a few and try them out. Otherwise you are looking for a 19 or larger in a mountain bike frame. Probably closer to 20 inch. A hybrid would work too and have easier to maintain components. I would stay away from anything with a suspension because that is more maintenance than you want.
I liked the above suggestion of Shimano Deore components as anything in that line will work for you as well as a well worded ad and a bike that doesn't look trashed. Flat tires, rusty chain, bald tires , shifters that don't work ... stay away. It will all be frustrating in the end. Good luck with your search.