Check with other long arm quilters in your area. Each area of the country charges differently. This will give you a clue as to where you can do your charges. Longarmers usually have a schedule of what they charge for each type and size of quilt. If your potential client then checks with other places they will know you are being fair in your charges. You also need to know what kind of batting they are using as some less expensive battings are not consistent in thickness and can cause problems if you are densely quilted. if you provide batting and backing that will add to your total charge.