I know of people who build a garage in Appalachia ( NY/Pa.),
put in a basement, and then chose to live in it.
Somehow they beat the zoning code for plumbing
and never got around to building the 'main house'.
Heh. There is plenty of that where I live. I confess that if my wife wasn’t against it I’d love to build a barndo.
https://www.google.com/search?q=barndo
Fact is, there are a lot of those around here and they can be downright palatial on the inside and quite attractive on the outside, as long as you don’t mind sheet metal siding and a slab floor. Check out the photos for yourself.