Do it, you will love it. Tearing down a dirty machine and rebuilding is a blast, and it sounds like you enjoy that kind of thing. As others have said, don't go in thinking you will make money, go in with the mind of a hobbyist. Be careful about buying a machine that needs game specific parts, ramps, toys, backglass, and sometimes plastics. They can be impossible to find. So, if you find something like that, research parts availability before you commit to buying the machine.