4. Play what the current market wishes to hear

By 'current market' do you mean the current folk market (whatever that is)?

I've never consciously done that in 40+ years of playing which includes folk, blues, jazz, rock'n roll and funk - sometimes simultaneously. I've just played whatever I wanted to play at the time, irrespective of fashion, and played for major periods of time in 4 bands in different genres.

One of the things that I've learned over the years is that, if you play well enough, with commitment and energy and constant practice, there'll always be people who want to hear you play - and always people who want to give you money - regardless of what you do. A market of one sort or another will always exist. For a few years I was 'professional' in the sense that I made enough to live on, but gave it up as it was killing the music in me. (Clacton one night, Southport the next, Hastings the next...).

However I think the term 'professional' isn't about whether you live on music earnings or not - it's about having a serious attitude and attention to the music, playing it as best as you can so that, wherever and whenever you play, you give it your very best.