How do you deal with friends who want your professional services for free?

I am in a situation where a friend has come to me and asked me to do some design work for him. I would love to do it, but from the conversation, he expects it to be for free. I said to him that since he doesn’t have any professional skills that I would need to trade, that I’d have to be paid. It would be a reduced fee, but still compensated for my time. If I were to hire a friend to do a job, I pay them, or exchange services. I feel as though my services are taken for granted and looked over. How do I deal with the situation and make him realize that I am serious about being paid?