I have made some quilts on commission. I don't mind doing it, if it's fabric I love and for someone I know. I only ever had one bad experience - a baby quilt I made ages ago for a woman who was an "internet friend" wanted it made for a friend of hers. She did pay for the materials, but she complained the entire time about how long it was taking. I told her it wouldn't be fast because a) I was a new quilter; b) I was a single mom and c) I held a very demanding full time job and went to school. Still, it only took a couple of months and I thought it turned out just beautifully. Of course, when she received it, she loved it and apologized profusely, but that didn't repair the damage she did to my reputation by bitching about me on the forum board where we both participated. The recipient of the quilt loved it so much she wouldn't use it. /sigh It was "too beautiful for a baby to mess up."
I've done a few more since then, but only for people I know and those I KNOW will love the quilt, like the one I'm making now for my husband's best friend. He commissioned it as a gift for his wife's birthday, and I'm only charging him for the fabric. I have one other I'm making for a former co-worker that wants to give it to her brother for Christmas, and she taught me everything I know about the field I'm in, so I don't mind doing it - and it's a fabric I REALLY wanted to work with. LOL But there's nothing wrong with saying No. I do it way more than someone might think!