I look forward to others' answers. If it was me, I would make something I liked that I know they would like (just in case, they have a change of heart) and then get started. That's how many professionals start- they need customers and clients- you never know if you are customer #5 or #500 unless they tell you. Apparently your neighbors like what they have seen so far and understand what goes into a quilt. I would also charge 3 times the cost of materials at a minimum. After it is done, you will not have been overpaid. And you can use that money to further your quilting journey wherever it takes you.