Nothing is clear cut in language but I think most people would agree that the word "professional" carries a positive connotation when used in the above way...therefore logically unprofessional carries a bad one.
In straightforward everyday English "professional" does indeed mean that you get paid for it, but "unprofessional" means you're a cowboy ... they're not, it seems, opposites, as you might have expected.
(And of course a (real) "cowboy" was no doubt professional.)