For me it would depend on how it was maintained. If the owner has records of that it will tell the story. How often it was serviced and what has been replaced. If they full timed a lot of things may be well used. Then again there may be a lot of things already replaced.
!50,000 mi. would not scare me. like said above check the tire dates and how old batteries are and have a mechanical inspection done, looking at brakes, steering, suspension, hoses, belts when the last change of antifreeze, transmission fluid and factor these things into the price. Like Doug said it may not be worth what they think it is. If it was well looked after it might still be a good coach for the right price. Good luck.