The back door of the place seemed sealed awfully tight when I first looked at it (move in day... I wasn't allowed in to inspect the place before it was given to me).
I did open it at one point. Probably not my smartest move, as getting it open (the hinges were seized pretty tightly, and the stud it was attached to was rotted to the point the whole door moved more than the hinges themselves) was not easy, and closing it again was worse.
Yesterday it flew open of it's own. Well... not of it's own, because of pressure from above, crushing the door frame and door. Looking at it I could see that closing it was going to take serious help.
Looking around it... well, that poor door and what remains of it's frame is the only thing holding the roof up. A friendly carpenter/neighbor who saw me struggling and stopped to help confirmed my fear. That roof is caving in. The siding began to visibly bow/buckle/bulge. It's not easy to get pictures without a ladder.
Ok.. so, my question (besides what in the HECK is keeping me from just tossing it all in and heading for the homeless shelter) is... where, precisely is the strongest support from below? If the flimsy wall won't support it, just how deep into the structure must I dig (the floors are not good here, and I'm assuming the framing is inadequate, or possibly even damaged). Are there diagrams of the structure of an old mobile, just so I can sort of get a feel for what's involved in this?
Not repairing it isn't an option. I've hitched myself to this disaster for better or worse.
How difficult can a caving-in roof tear-off actually be???? 
