I would advise not to buy anything prior to retirement. The RV snowbird lifestyle has many ups and downs and each area (state) has it's pluses and minuses that you may not understand until you are totally retired and "living the dream."
Remember a Casita is usually only the size of a stall and a half garage. Imagine living in that, plus having an RV that is aging in the drive way. That is what really is happening once the pictures are taken and marketed on the websites.
True real estate is currently giving a much better bang for the buck right now then the dream of the RV lifestyle is. Most RV lots are only 35 feet wide, which really isn't enough width given their asking price. Without a doubt they do offer a community atmosphere, but so do many 55+ gated retirement developments.
In my opinion, invest your current income, then buy an older RV and see the country when you retire (do the adventure you're currently seeking,) then in the second half of retirement buy a S&B in a 55+ community that isn't too far from family, and enjoy that part of your life in a solid secure abode.
YMMV