I think the larger units are the most interesting. The chances of fostering success go up linearly with more entrepreneurs but there is also a much greater chance of having synergistic effects.
They need a lot of work, of course. That's OK; given some startup capital (I suppose this would be metastartup capital) I could easily do a reasonable job of making them livable, then comfortable, then nice. It wouldn't even cost all that much - even if I hire people to do the work. The Amish are only charging $9 an hour right now; there's just not enough construction work to go around.
I think the larger units are the most interesting. The chances of fostering success go up linearly with more entrepreneurs but there is also a much greater chance of having synergistic effects.