Well you earn money by doing side jobs or little mini games such as mowing the grass, picking up trash, doing kill fests stuff, etc.
Basically you are a ranked assassin and you need to move you're way up to number 1.
But NMH2 is about you were number one but it now takes a couple years later. You have moved back to like rank 50 and now Sylvia wants to to come back. Plus you need to fight for your best friend.
You do kill alot of people but it doesn't feel repeative.