My son is a good artist and is often taken advantage of because of his talent. He is currently a sophomore.

My son is a college sophomore who is artistic & majoring in animation. Many relatives have been requesting him to draw logos for their businesses and/or draw designs or pictures of their dogs as birthday presents. He never says "no" to anyone. As a parent, I resent them doing this to him; especially when they don't pay him! How can I advise him so he can tell them tactfully that he cannot draw for "free?"