First, buy an "America The Beautiful" pass for the National Parks/National Forest/National Seashore/Army Corp campgrounds/Bureau of Land Management lands/ and a few others I have forgot. Its money well spent. If you are over 62 the senior pass will also get you reduction in fees such as campground costs.
Go to Youtube and look at some of the videos on proper etiquette on overnighting in Walmarts (where it is allowed, some places it is illegal, others the managers simply won't allow it), Cracker Barrels, etc.
Here is one done by Sean and Kristy of Long Long Honeymoon
https://youtu.be/sVvScIscBdoFuel mileage, forgot to add, I kept telling myself that I would not tolerate single digit fuel mileage if I bought an RV, and I ended up buying a Sprinter chassis Class C, and get about 17½ mpg average, but I sometimes wonder if I should have not done something different, as the Sprinter is a quirky vehicle to say the least.
Charles