This is all good stuff for when you are looking, but there are some things to consider when you've found something. Buying a non-running bike is almost always a leap of faith in terms of believing what the seller is telling you. Lost titles can be a red flag, but I've bought probably a dozen or so bikes without titles without problems (AZ is particularly easy for getting a title, and none have come up stolen). Cosmetics matter if you want to keep it original; the prices on tanks, side covers, etc., have gone up in the past 10 years or so significantly. For non-running bikes my gauge is whether I can part it out for the price the seller is asking if it's a non-running bike. If it's a runner, you want to let it run and warm up, and do the obvious: listen for weird sounds, watch for leaking oil, run it through the gears, make sure it stops, look for signs that it's been down, etc.