Gone Pro

A fan who becomes a professional writer of SF has "gone pro".

Many fans, especially in the earlier days of fandom wanted not only to be fans but also to write professionally. For the most part they did not leave fandom, but added a professional career in addition. The list of fans who turned pro, but did not leave fandom is very long: Bob Tucker, Ackerman, Fred Pohl, C. M. Kornbluth, Poul Anderson, Hal Clement, Bob Silverberg, James White, Jack Chalker, George Scithers, Patrick Nielsen Hayden, Mike Resnick, and literally dozens of others.