I have organized 21 retreats in the last five years (four retreats a year, Feb., May, Sept., Nov.). They are called "Intown Retreats" because everyone goes home at night. We have them Monday through Thursday, from 9 a.m. to at least 9 p.m., and there are usually 15 to 20 of us. Everyone brings some type of food dish, and we sew, visit, laugh, eat, etc.
The place we use is a subdivision clubhouse, and it has tables and chairs. The room is safe, so we leave all of our machines, projects, etc. there overnight. The room costs us $300 for the four days, and we pay $50 for someone to come in and clean up the room. So, it normally costs us each $7.50 each a day. What a deal, and so much fun! Sometimes we bring things from our sewing room that we don't want, and we have drawings, and each person gets to go home with a new treasure.