Contracts should always be used for any kind of free lance work. Good example, my daughter, a singer, was asked to sing a few songs for a charity event for an agreed upon price. Then they called and ask if she would also MC the event for double the money. She agreed and performed the event and everything went great. Everyone loved the performance and the person who hired her said she was the hit of the evening. To make a long story short, they never paid her. And they haven't returned her calls. Lesson learned - define the expectations in a contract.