I think there's always a difference between "selling fanwork you made" and "being commissioned to create fanwork". The first one is illegal where I live, but I guess you could find a loophole with the second because you get paid for the work/time you put into it and not just for selling copyrighted material you already created.

So getting paid by people for showing them a fanfic you already wrote? No.
Getting commissioned by people to write that one fanfic they want to read? Yes.

And I've actually seen a lot of people do fanfic commissions. I don't see how that is such a revolutionary new concept?