I was thinking about the same thing lately, except instead of living in an RV, I'd rather it be a houseboat. Seen a show on TV a few weeks ago that showed high end house boats. You can actually get something quite nice for about $400,000 US, but they had ones that were as high as 2 million.
You'd basically be replacing property taxes and house maintenance with slip fees and boat maintenance, but it would be nice to just pull up anchor and move your entire house to a different location if you had the inclination.
edit: I think this was the company on the show:
http://www.lakeviewyachts.com