The first time you soak your shoes while emptying the tanks, you will know grey water from black.
I guess I have been around long-enough to say welcome.
A used Class C is a great place to start. I don't know enough about brands. PPL in Texas has a great website where you can look at used RVs, photos, equipment lists and floorplans. I am sure there are other resources as well.
From observing the experiences of others, I would not get an old Class C, from the carbureted engine days, unless I was a good mechanic. As far as the appliances, they just plain break from time to time. Keep some cash or credit handy, for emergencies.
+1 on avoiding RVs with leaks, unless you have the means and talent to do the repairs - they can be major and the damage almost completely hidden.
Getting a fair deal is important, but concentrate on something well cared for. You will likely forget what you paid in a year or two anyway. We have purchased three motor homes. Each time, we knew when we had found the right one - an open and sincere owner (or dealer), frank answers to the questions, and a clean and well-maintained unit that seemed inviting to us.
I would not hesitate to buy a unit with a bad refrigerator or etc., if the story fit into a pattern of care. There are very few individual items on an RV that cannot be fixed with a few dollars - a pattern of long-term abuse could make the RV worth less than nothing to you. A bad engine, bad transmission, bad generator - pick two of the three, and do some quick research to find replacement cost and you will know what I mean.
Matt B