I went full-time in the early seventies, foolishly thinking I might as well get paid for doing what I enjoyed most. I soon learned a couple of salutory lessons:
1) A professional photographer's life is probably 5% taking pictures. The other 95% is administration; setting up shots, finding locations and/or props, models etc, accounts and book-keeping and, most soul-destroying of all, chasing people for money they owe in order to finance the next job.
2) I'm a good photographer, but I'm much better at taking pictures I want to take than the pictures that others want to buy. Call me stupid, but it took me a while to recognise the difference.
I had some fashion stuff in the colour supplements and a good few spreads on the fashion pages of the daily press, particularly the Evening Standard, but lessons 1 & 2 dispirited me to the extent that I reverted to my amateur status after two and a half years and became an academic instead.