You MUST talk with the person before you start. You will have a basic idea of how long it might take to assemble the top, to sandwich it, and then to do a minimum of quilting. First, tell them the estimated hours involved, then approximate what additional materials will cost. At this point they will have an idea of the very basic costs. Now you can discuss what your labor cost should be. Preface it with 'I don't think I could make it for less than $???, probably closer to $???. They will tell you if it is workable or not. Also, if you want to or can do, offer to help them to do it. But, PLEASE, do not start it without that discussion - especially if it is a family member!