I own a start up magazine. I had a guy that agreed to help me by writing articles and editing. The verbal agreement was that he would get paid when the magazine began to bring in revenue. He decided to leave and now is asking me to pay him $500. As a friend I told him "we have a verbal agreement and by you asking for payment when the magazine has not brought in any money is breaching our verbal agreement made." All of this conversation through Facebook messages.
My question is if he tries to sue me for $500 does he have grounds to do so since there was a verbal agreement in place?