I used to rent time on a long arm at a shop near my house, sadly they closed recently. She had 3 Gammill machines, and only rented one of them. She quilted for others. I did have to take a class and buy the zippers to load the quilt. The zippers cut the loading time quite a bit. I usually could finish a small--twin sized quilt in about 4 hours. It is kind of hard to quilt for 4 hours because I have a bad back. It was also somewhat inconvenient to plan ahead as to when you wanted to go to the shop and quilt. I really enjoyed quilting on the big machine, but only could do pantos. I'm sure it would take a lot longer if you wanted to do free designs. Your idea sounds wonderful, and I wish you luck if you decide to go with it. Wish I lived closer to you.
Sue