Good quesitons for a longarmer. Turn-around time varies by longarmer and depends on who is ahead of you line, size of quilt, and complexity of quilt design. My turnaround time is 2 weeks.
Cost will also vary with longarmers and again depends on size and complexity. Usually the least expensive is to do an edge-to-edge (E2E)quilt design which is what most quilters want to keep their costs down. E2E looks wonderful and truly enhances your quilt.
A customer can provide their own batting or usually the longarmer will have batting on hand for purchase. I include batting free on the first quilt a customer brings to me to be quilted.
Jeannie in Phoenix
Gammill w/Statler Stitcher
http://www.InThePinkQuilting.com