@Tone From what I can remember, the best states in the US that have cities without building codes are Colorado and Arizona. Missouri has some places where the codes aren't enforced, but eventually that could change and they pop up and start messing with your digs.
I'm not for tiny houses portable houses. They don't make sense. First of all, you have barely any space and no real toilet, and you spend $25,000 building a house about the size of a small bathroom. I think it's for hippies on Instagram.
RV is much more efficient and will always be. You can get your solar panels set up, Starlink for internet ANYWHERE, cook food, and use an actual toilet. You have a bed at the very least. You might even have like 2-3 hidden beds for company. Or animals. I knew an old vet who sold deer, beef, and elk jerky on the side of the highway out of his RV. He sold each pack for $12-13. As a teenager, he gave me $1 for every one I sold. Made $22 in a couple of hours and that's how I found out he did very well for himself.
If I were to do this I would probably just get a mobile home and put it on the property and then make it as sustainable as possible. Sometimes people give them out for free, even though moving them can cost a few thousand depending on the distance.
I think the cob house has to be on something like wheels. I wonder how well it would work to take apart a junk RV to use as a foundation and build over it.
Edit: I have an uncle that had a bunch of old school buses. He used to convert them into cool places for his kids to hang out.
You might think a wonderbag is pretty cool, too.