The engine will last but the coach isn't worth it

My good friend has just finished parting out 3-4 motor homes and trailers. All were mid 80s to mid 90s vintage. Their owners had just quit using them and left them set out back and rot away from roof leaks and water damage. Water stained ceilings, walls, and soft rotted floors. Appliances rusted. Drive train still some value but not much else.
So---from seeing this, lesson here is repair/keep the roof in good shape or park under cover or inside if at all possible when not using.