You really are a good writer, why don’t you start a thread some time on " paragraphs from a book we are working on" Just post one or two paragraphs. I have the opposite problem, I love to write but I am a terrible writer, so I really do write like I am stranded on the moon.
Outsider
Artist.
I don’t see the need for a qualifying adjective.
Look back at the example of “musician”: all the time, especially on the internet, people describe themselves or others as “semi-pro” or “full-time professional” musician. I still don’t know what that means. In my experience a “pro” spends a lot of time teaching, or selling books about teaching, and in some cases probably spends as much time on stage as a “weekend warrior.” Or they’re on the road 340 days a year living out of a suitcase or a glorified van by the river. That’s a “pro” but very different lifestyles.
You’d have to look at their 1040SE forms to see what’s what.
IMHO none of those are useful terms, so I’d stick to the neutral “artist.” Any further inquiries should be directed to their accountant.
I like ‘side-earnings’ or side-income’ for the actual money from a ‘side-project’. Pretty neutral.
Rather than labeling the artist, you could label the product: “Non-monetized content”.