Conrad, I think you may have missed the point here. Unless I have misunderstood,a house concert IS open to everybody who finds out about it and all are welcome. It IS a paying concert for the performer-- he gets the "gate". The owner of the house has done a NICE thing, he has provided a place for the musician to give a concert without having to rent a hall and make local arrangements.
I still haven't met Rick F. although I was looking forward to soing so a couple of weeks ago at Annap's Gathering. I bought my copy of "dreamer" from our own Dick and Susan last weekend at NEFFA and it's wonderful! I would go to see Rick (or a number of other people) in a large concert, in a small house concert (and expect to see a concert) or at a party and expect to share lots of songs. I agree with you that it would be inappropriate for somebody to charge admission to their house for a song swap. . . but I don't think this is what was meant here.
When Rick said he plays better in a non-bar-- been there myself, done that and no matter how hard you try, it's very hard to give your best when people have come to drink and not to lsiten. There IS an interaction between listeners and artist and one somehow plays better when people are listening intently. (Interestingly, nursing homes, which can be almost as noisy as bars, I find rewarding but draining) YMMV