Ian,
Without speaking out of school there are several people on the 'Cat who play or have played professionally. Art is retired from the road, but he was a real road dog for many year. Could be he never held a "real job". **grin** NOI.
Rick Fielding is a Canadian performer who plays full-time for a living.
Sandy Paton and his wife Caroline have been picking and singing professionally for more years than they want me to mention. They also run Folk Legacy records. So one of them is the "day job", but probably no one knows which.
There are a few more full-time players out there, but the names don't come to mind right away. Hopefully, at least those who are already "out" will post.
Roger in Baltimore