A lot depends on the year the MH was manufactured. If it's a pre HUD (built before June 15, 1976) up to 1979 there's a big difference in the way they were manufactured and the types of materials used. Most pre HUD homes-circa '79 were 2x3 exterior walls and 2x2 interior walls.
They were aluminum sided and used 3/16" photo finished veneer siding on the inside. Doors and windows were smaller and many used aluminum extruded frames which are no longer made and the ceilings were sprayed with popcorn.
Here's a '78 one we're trying to remodel right now:
The roofs were a rolled metal material laid over a very lightweight and flimsy 1x2 and 2x2 truss system that was extremely fragile and vulnerable to damage from falling tree branches, hail, and if a repair man didn't know how to walk on them the trusses were easily broken. The average floor (section) weighted around 10,000lbs or less and the list goes on
But whence getting into it here's what we finally had to do:
That's not to mention the caustic and carcinogenic materials and chemicals i.e. formaldehyde and asbestos used in the particle board sub flooring, countertops, insulation and ceiling materials, etc. In many cases the best place for a PRE HUD-Circa '79 is the nearest boneyard.
Finally after removing the siding and discovering that the rim joists were all rotted out this is what we have now:
Why not just remove and replace with new you ask? Because of the existing setbacks. Presently this home is legal non conforming (grandfathered). However, once the entire structure is removed then it can only be replaced with a much smaller park model which would drastically reduce the SF.
Now you're probably wondering why we took this project on at all right? Quite simply, because it's only 300 feet from the oceanfront and less than a 3 minute walk from one of San Diego's best surf breaks. When finished this can be resold for about $250k or rented for about $2500/mth.
Good luck!