The ones in the black forest are usually too cramped to be of much use. I occasionally run into a mostly intact one. They're usually four floors tall with a thatch roof stuck on the top and barely any room to move aside from the stairs/ladders in there.

The ones with the walls knocked out are more useful because then it's easier to expand the second floor into a livable size. They seem to come in three sizes but all three are too small to be comfortable.