To answer the Q about limiting number of attendees:

Most (or possibly all) of the house concerts I've played are "invitation only" and/or "1st come, 1st served".

To me, the coolest part is the intimacy...you're about 3 feet from the entire audience!...one I play in N. California is in a big octoganal room (used to be a ballroom in the '30s, I'm told).