I'm only half way through this thread, so I don't know whether this has been mentioned. I hesitate to mention it, since I'm not on the same pay scale as the more 'senior' posters.
You are probably aware that the very best music teachers avoid teaching any songs or other complete works. Rather, they insist on relentless practicing of scales. And this is so their students can get on the right pay scale for any gig.
The best paid scales are G major, E flat minor and B flat. (This is why Hendrix tuned down a half step, and why brass players are always so horny).
Then there are the unpaid scales: F, A flat, and so on.
The ones to avoid are the pay to play scales, of which the most expensive is D minor.