We are also new to RV'g, and after a year of research went with a Toyhauler for the extra room (garage) and also we found that almost without exception they come with a generator as a standard. Or at least as an option that everyone seems to take (we bought a used unit). Probably TH's are more likely to be used boondocking.We're anxious to get on the road in a couple months.
It is that same Onan 5500 and while we haven't slept aboard yet with it running, I have had it running for a couple hours at at time while working inside and it seems surprisingly quiet.
As far as the standalone units I've seen the 3500's at Home Depot and Cabelas pretty regularly for $400-$500.