As a rule, I don't do commission work, I told him. Why not, he asked. Well frankly, I just don't have the time. I work full time as a videogame designer, sometimes more than full time. I have to carve out whatever spare moments I have to do my own personal art work. So I really just have no extra time on top of that to do artwork for others. Sorry.
Oh, yeah sure that makes sense, he said. I'm sorry to have bothered you, I just think you're an amazing artist, and my stunningly beautiful girlfriend and I were hoping you would sketch her nude.
Obviously, as it turns out, it's more of a guideline than a rule.