We are retired in our 40's and fulltiming in an RV. It's awesome.
My perspective is from a couple that does things on the frugal (as opposed to on the cheap), plus who likes to park the rig in one place longer and do exploration day trips, thus saving gas money. We are set up to be comfortable wherever we are, whether we are parked in an RV park, in a federal/state/local campground, or in the middle of nowhere with no hookups (it's called boondocking in the RV world).
1. Solar power is the way to go. We have 750 watts of solar power on the roof of our motorhome. My husband put the entire system in himself after we bought it. We can go indefinitely without hookups in reasonably sunny weather, although we like to take on fresh water in our 80 gallon fresh water tank every week or two, plus dump the waste tanks. If you don't have any wish to boondock, you may not need this option.
2. We decided to purchase a Class A and a toad (towed vehicle), mainly because we just did not relish driving a massive tow truck around all the time.
3. Whatever class of vehicle you choose (Class A, Class B, Class C, fifth wheel, travel trailer), do your research on that particular setup, and then walk around inside a lot of units before you make your choice. Depreciation is such that buying a motorhome used makes even more sense than buying a passenger vehicle used.
4. The only way to learn all the tricks is to do it. I did hours and hours of research, yet I learned so much more by doing.
5. It takes a while to realize how flexible this lifestyle is. Even if you're in it for a short time, e.g one year, you can do/go/stay/backtrack/drive all day - whatever or whenever you want. That is the true beauty of this lifestyle. If you don't like where you are, just pull in the slides, retract the jacks, and drive off. If you like where you are, stay another week.
One of my favorite fulltiming bloggers, Laurie Brown, did a good series on buying an RV:
http://laurieandodel.blogspot.com/2009/04/buying-rv-motorhome-or-fifth-wheel.html#uds-search-resultsGood luck!