In the city I’ll be working in, they follow International Residency Code, or IRC. IRC requires:
a permanent foundation,
a main room of 120 sq ft or more,
every other room (including bath?) to be 70 sq ft or more.
Total requirement: 190 minimum or 260 with a bedroom. I believe that’s within the realm of possibilities, especially when I was considering 300-400 sq ft.
The most interesting part of my day? My chiropractor has looked into Tumbleweed tiny houses, himself. My director and his wife are considering a very small home (less than 700 sq ft). Apparently, the idea of living small is getting BIG!