[folivier]

A used coach needing batteries and tires is not unusual, most people when selling won't put out that money for those.
Lack of use is a negative.
Bay doors could just need new rams, there is a post on a homemade tool to easily replace them. The electric locks are easily and cheaply replaced.
Newell typically used higher quality furniture like Villa.
I would plan to pull and reseal all of the windows, not difficult but time consuming.
Generator not starting is probably due to low fuel level.
Possibly the speedometer/odometer is not working? and may have more miles than that. If it's a Series 60 and has the Detroit monitor it might show the correct miles.
But like Clint said, have $$$$ ready to spend on it. And time, are you wanting something to use now or have the time to redo it like you want?
Another weak spot is the radiator, look at it closely for fin rot.
IF you are someone who enjoys and has the skills to do your own work you can do most of these needed items. But I'd look for a coach that has had better maintenance.
Have fun!