Marion, I think you've hit an important nail on the head:  "...volunteer gigs are quite different from what I would expect a paying gig to be - much more on my own terms...  ."  and "It's [the] extra headaches that I want to be compensated for - not the music itself. "  [Like all the red tape that hospital required.]

You're right that "waiting for the next call out of the blue isn't a good plan."