If I were to ever sell a quilt again, it would be one that is already made and I feel like parting with it. I know that you have a special situation, where the person is using shirts, but you do want to consider your time as well as the materials involved. I have heard of others who were asked to do this, and the buyer wants to pick the pattern, the colors, and then they want in three weeks for their cousin's wedding. Get any agreement in writing, and something up front.