stfoth---exactly correct. How could McCartney have been poor?! He’s by far the richest of The Beatles. But he knew he didn’t have to pay his band well---he could get anyone to play for him, no matter how low the pay, just for the exposure to a mass audience that would result from doing so, to increase one’s visibility, to make a name for oneself. Denny Seiwell came from the L.A. studios (as did his current drummer, the great Abe Laboriel, Jr.) and Jazz clubs, to which he returned after leaving Paul’s employ.
And you too are right, schubert. I should have qualified musicians with the adjectives Rock, Blues, and Country. Jazz and Classical guys are a whole ’nother matter!