1)I mean his phone bill alone last year must have come to twenty G's (he's got lines open to all the tracks and ballparks all day long, you know), but only ten years ago he would have had to sweat blood before he coulda raised a lousy fin.
2)But they were extremely fond of Max, anyway. He didn't push, he was always good for a fin, and though he never complained, it had been hard for him since his wife died.
-The Apprenticeship of Duddy Kravitz by Mordecai Richler -
I looked 'fin' up in the dictionary. It means a five dollar bill in slang, but it doesn't make sense here. What is the meaning of 'fin' here?