Used cameras are the smaller version of a used boat, it starts out simple enough, just some hardware and new paint, bellow, canvas, new keel, a couple of weekends and it's done.
In reality it's not that simple, ask how many have these are in shoe boxes sitting around unfinished. Be realistic about the repairs and the time to do them. It may not be worth it in the end. If it's replacing a bellows and cleaning up the finish that's one thing but a compete breakdown with making and replacing hardware then that's a different story. Keep it simple. If the back is good and the basic mechanics are good then it might be worth the effort. 5x7 puts it in a higher category than say 4x5 were the cameras are abundant. Do you have holders?
The best of luck,
Curt