Box and papers aren't really important unless they document significant provenance, like if you have a receipt showing that some famous person originally owned the watch. A watch with box and papers is worth slightly more than one without, but that applies for both buying and selling.
All mechanical watches will need periodic servicing, and any second-hand watch could have an unknown service history. Obviously, more expensive watches are more expensive to service, so that should be an automatic part of your purchasing decision.