Not sure where you all live, I'm in California but I thought that you had to go through all the building permits to put any structure down on your property? Are you planning on just putting these structures down and hoping none of your neighbors see the structure and report you to the county?

I think the only way around spending 10 to 20 thousand dollars on building permits is to have the structure on wheels or a trailer, like a tiny home. But even this, in some counties has reatrictions.