We’ve watched Tiny House Nation, where they custom-build homes with a ridiculous amount of secret compartments, extra storage and dual use furniture. For two people in a part of the US where you can be outdoors nine months of the year, I think two people could be happy with under 500 sq ft and a decent outdoors space.
We’ve also watched those House Hunters International shows on buying a pre-existing tiny home. For parts of the world with four seasons living, I think a 650 sq ft one level home with a backyard space is the minimum required that we’d need to be happy.
I can’t imagine living in a tiny home with two kids, a spouse and one or more pets, but somehow they find people willing to do it in under 500 sq ft: