Does a used mobile home have to sit on a pad?

I don't know it there are general rules about it, but it's certainly very advisable.

There are often jobs that have to be done under one. In most cases, even operating your main shutoff for water. (-Would you like to have to crawl into a muddy swamp in winter to do this ) The units are also qwuite heavy and should sit on a concrete pad just to keep stable if nothing else.