What do you mean by professional or what is your definition of a professional artist? When I hear this term being used I think of an artist who has trained in their particular area. Example, portrait or landscape where the application of their knowledge and understanding of the requirements to do quality work is required. They need to understand how to mix colours properly. They need to know how to draw well and how to prepare the surface they choose to work on. They spend lots of time in the studio perfecting their skills and studying art from great books and if possible, visit galleries and good art shows. This is a job not a I'm not in the mood today so I won't paint career. They approach what they do as a professional not assuming they know it all....you never do....always learning. This is what I would call a true professional artist and it usually shows in the level of their work when you view it.