Since he clarified he didn't mean "RV", but rather a mobile home...
It's for sure possible. Some mobile homes may have OSB, or maybe even particle board flooring, so check it out first. A little water, OSB, and a stand with only few points transferring weight will go right though. Due to the steel undercarriage it's otherwise likely as good as most houses, but you'll still need to judge the size of the tank and where it will sit. Also, if you're not on a full foundation a large tank could cause settling on one side. If it's sitting on stacked 2x4's, not a good idea.
Just put it on a full walkout basement and build a room for the tank downstairs :)