The main issue I see is the land and utilities. Land can be pretty expensive, and so would installing the utilities.
I personally would just get a camping trailer/motorhome. Probably more cost effective (first video estimated $12k total cost, which was half of the usual estimate for one that size, you can get a lot of used RV for that price), self contained (more flexibility with where you can park it, and doubles as an apocalypse survival shelter), and they have a lot of space saving features, which may be hard to replicate. I've actually thought of living in one after the military, but that would only be if I'm single at that point, which is looking unlikely.