If there's no visable rot, ceiling paneling not bubbled or soft jack attachments solid and appliances WORK without leaking gas, etc side walls solid then you have potentially "good bones" to work with. Having just finished some rehab on our older camper be advised that the repairs can get expensive. Aged plumbing can seem fine till pressured up then the leaks will start. Test water lines with 12V water pump not city water as its quicker to cut the water supply off and reduce flooding. Been there done that! Ours has definitely been worth the expense. Those bathrooms can get expensive and the wait times for component delivery can be long. Good luck.