well the OP is probably not around here...but i will add my 2 cents as this is an issue still needing discussion.
i am thinking a way to get around building codes is to build "agricultural buildings".
now codes vary greatly with state and county, so you have to read your
local town's bylaws and anything you can find in your state. i'm sure theres a lot of variation between the people who do inspections and if they are lenient and just trying to help a person make a structure safe, or if you get the one guy in the town who will make a huge issue of a small meaningless thing.
actually just living the way i naturally want to live anyway, with bazillion of plants and growing as much food as is possible, makes it a bit easier....to play off the agricultural building angle, of which there are usually little to no over sight of....or restrictions on. again this is is highly dependent on your location. being very rural helps. even in most residential areas, small farms are allowed and given a much easier time getting "accessory" building permitted or told they dont need permits.
since i want to build a tiny house, with a huge
greenhouse, i believe i may be able to hide that it is actually humble living space within. so a potential plan i have thought of is to play off a building as just being for growing plants, as a small farm...basically as though it is only for support and a purpose related to growing food..
people are allowed to own a piece of land without putting a house on it ...and to have a small (or large) farm on that land, even in many residential areas that have pro farm laws on the
books.
and if the smallest part of the "agricultural building" looks a bit like a kitchen/living room...well that is not unusual for its a space for people to be when they are not working on stuff, and having a kitchen food storage area when growing food makes perfect sense. not having a nice bathroom, etc...things people would do anyway when building a small structure on a shoestring...changes the way it seems.
some states (many that i have lived in and read local codes of) have an exception for farm buildings and anything used for growing plants, used to house animals etc. while you might want to at least talk with the building dept. to let them know you have built it or whatever, and get an ok to go ahead and build a small shed for some agricultural stated purpose.
but not calling it a house rather an agricultural building, or
greenhouse, or barn. not all towns and states though have these kinds of exceptions.
another loophole is to build under 200 sq ft . some places i have been the limit is 300 sq ft. anything under 300 sq ft does not need a permit.
other people build up on wheels because things on wheels dont need a permit. however some places wont even let you have anything on wheels, or if so only temporarily. building rural helps again in that respect.
now maybe none of this addresses the OP, but i am thinking they arent around much. i have never heard of a place that wouldnt allow small simple sheds and such, and it seems strange to me that they would require a regular house and septic before allowing accessory buildings. these kinds of things are highly localized though, so its your town and the by laws that you must follow...