Flippin heck! I was going to say it's probably cheaper than a holiday caravan, but maybe not.
I do think being able to make a home out of anything you can get hold of is a good idea, but I always get put off when these articles and blogs are presented by the god squad folks. It's just me though...
Interesting idea. I've seen the same sort of thing buried underground as a BOL. However, if you want something overland would it not be better to look at getting a 2nd hand static caravan? It wouldn't look so suspicious when siting it. You could then repaint to camoflague it. IMO