Re: Were they paid?
Some sort of monetary system is definitely in place.
From TOS: The Apple--
KIRK: Trying to get yourself killed. Do you know how much Starfleet has invested in you?
SPOCK: One hundred twenty two thousand, two hundred--
KIRK: Never mind.
Curly: Oh, you hit Santa Claus. Just for that, no toys! --Wee Wee Monsieur (1938)