The first time I saw the multi-inch gap at the bottom of a mobile home interior door I thought some really bad carpenter had been at work on it. Of course, I learned later the large gap at the bottom of every interior door is deliberate and provides the cold air return to the furnace.
The doors are built on jig’s at the factory so they start out square and plumb. However, transport, setup and usage can quickly change that. By loosening the hinges at the door side or the wall side some adjustment is possible and you may be able to fix a sticking door easily that way.
In repo situations they seem to be a favorite target of frustration and are often smashed in and torn off the hinges. They are cheaply made and easily damaged. If there is major damage I would price new doors at a mobile home supply place before I went to a lot of work trying to salvage the old ones.
I did some really nice repair jobs until I figured out it was a lot cheaper and quicker to get new ones. The mobile home supply places also sell sticks of the quarter round used as door stop in colors that sort of match the wood grain.