The thing is that, once you assume a standalone single family house, the savings associated with going "tiny" vs., say, 1000 to 1500 sq. ft. modest just aren't that much and the compromises are significant. In general, there are certain must haves. A bathroom, some measure of kitchen, a place to park a car (and, yes, in most places where we're talking standalone houses 1-2 cars need to go somewhere), a bed, at least a desk, etc.