There are a number of options you can do for a generator:
If you want a boondocking setup, you can get a rear hitch receiver attached to the frame (do NOT use the rear bumper), a cargo rack, and a security chain, and put a generator there. A lot of people have had great luck with two Honda eu2000i twins with a parallel cable and an extended run tank. You can also use a larger generator like a Yamaha 3000seb or a 4000-6000 watt model that can saturate a 30A link. However, the larger models are heavier. Other people have had complete, lockable enclosures fabricated so that the generator is properly vented and cooled, but out of sight.
Another alternative makes life easy, but it requires a lot of RV service. Estimated cost would be $7500.00 or so, and it would have to be done by experienced professionals. This would be having someone fabricate an enclosure for an Onan MicroQuiet generator so it sits underneath the RV. Then it gets wired in via a transfer switch (so that plugging into shore power disconnects the generator electrically), and connected to the propane lines. The advantage of this setup is that once in place, you can start/stop the generator just by flipping a switch in the coach.