And along those lines, it's basically impossible to build legally a true granny flat, with a 2nd kitchen and separate entrance, anywhere. Some mega-mcmansions are built with servant kitchens, but for most development it's illegal. It's possible the reality of the aging boomer demographic will put some pressure on politicians to change this in some places, but I doubt it.
...adding, yes, in older towns and urban areas there are plenty of existing granny flats, though even in these places it may be difficult to build new ones, and it appears Portland's cool with them.
