Where did the money come from?

[mrsbrooksathome]

No: HPFGUIDX 90527

Here's a question that has always nagged at me: In the first book, 
Hagrid tells Harry about his vault and all that good stuff, and on 
numerou occasions throughout the series, Harry having more money 
than Ron  is an issue.  Where did the money come from?  I know Lily 
and James supposedly left it for him... But where did they get it?  
And has anyone ever mentioned what they did for a living?  I know 
they were in the OOTP, but as I understand it, that is not exactly a 
paying career? Ideas?