We always run a merchandising table at any gigs we put on, staffed by one of our volunteer stewards. (Occasionaly the artiste's partner might want to do this). Any performer can entrust us to sell their CDs for them. Never come across anyone objecting to support artiste's CDs being sold, even from the same table.
As an aside to this, we have sometimes asked for 10% of any sales to be donated to our festival funds, and/or a CD to be donated to the mandatory folk club raffle.
And as a further aside, I was more than delighted when our last headliner very kindly gave me one of her CDs for having done the selling job that evening.