The least expensive RV would be either a Travel Trailer (TT) or Fifth Wheel Trailer (5th Wheel or Fiver). You can find well cared for used units on RVTrader.com, Craigslist or Facebook marketplace for reasonable prices. If you don't plan on moving from one RV park to another often you can hire an RV transport driver to place the unit on your site at an RV park or campground.
New RV'ers tend to choose smaller units because they are often intimidated by the size and ability to tow such a large RV. I always advise to buy the largest unit you can afford because if towing you will become comfortable with the size after just a few trips. My thinking is I would rather be cooped up in a 30 plus foot RV versus a 25 foot or less RV if the weather is so bad you are stuck inside for several days (think hurricane Dorian). Cabin fever kicks in very quickly.
30K will get you a very nice used TT or Fiver plus a truck if you will be towing it from RV park to RV park.