Actually, many travel trailers and fifth-wheels are factory-equipped with a compartment and wiring for a generator option. Due to the lack of on-board gasoline or diesel fuel, most gensets for RVs are propane-powered. This makes having large propane tanks essential, since the same fuel supply will also operate the furnace(s), hot water heater and fridge.
A recommendation: Consider having solar panels and an AC inverter installed. They will supply just about all the AC power you'll need for operating everything except the roof air conditioners, and will do it completely silently. That will allow you to "run silent" most of the time, reserving the generator for battery charging and occasional air conditioner use. Most factory-installed solar panel packages are crap, but the aftermarket has some excellent packages.
Here's a non-profit group that can quickly get you up to speed on All Things RV:
[url=http://www.escapees.com]Escapees RV Club[/url]
Best RV club going, by far.