I don't think they make much, I think that job is more about being schooled/groomed. A young guy who could handle himself would drive around a boss or a big captain and learn stuff from them, attend sit downs, meet other high ranking guys, listen to high level talks etc.
Like the Chin with Vito Genovese or Billy D'ellia with Russell Buffalino. Both were groomed and later became bosses.
Donnie Brasco was the perfect example. Unfortunately he was not who they thought he was.
