Whenever we let our kids invite friends we paid for everything as we are "inviting" them. I would never expect my guests to pay anything. The only thing the kids had to pay for were souveniers. When we take a friend for DS skiing with us we pay for another room just for him and a friend, all ski equipment if needed, food, lift tickets, hotel, and anything else that comes along. If I couldn't afford it then I wouldn't invite anyone else.