I have a 31' class C (with a front-driver-side slide), Ford V10 (7-8mpg), and no tow. We travel with 2 adults, 3 kids - two of them teens. The dinette, cabover, and couch does the trick for the kids. It's plenty of room. It is sometimes inconvenient to not have a tow vehicle, but there are ubers, taxies, rentals, etc. Most of our trip planning can work around the need for a car.
My experience has been just this one RV, and I bought it used. If I had one thing to say is that you should be absolutely picky to the extreme when buying used. People will hide the leaks, breaks, and flaws so you have to ask the right questions and make them prove everything works. I didn't know enough to really determine if everything worked so I paid a local RV dealer $200 to check it out for me. They said it was all functional and when I bought it and got home some things did not work (the water system for one). If you have a knowledgeable friend, bring them with you. If you pick something up that needs a lot of work either you have to pay or fix it yourself. No matter what (even buying new), prepare to be a handyman, capable of sealing, de-winterizing, etc.
The maintenance is the most important part. Without it whatever you buy will fall apart under you. While spending a lot of time fixing/paying for the issues on mine I have become serious about maintenance because I can see that is what caused the problems to begin with.
The good thing about Class C is that they're the right size, and being a truck chassis you can do some chassis maintenance yourself if so inclined. The brakes, filters, and oil are just like a car.