Well I wanted to do this mission the right way at least once. It doesn't matter if you talk about Corvinis debts with Querano the first time, he'll still offer to team up on the the two gangs.
To get this mission properly filed & finished, you have to team up with the police after talking to the gang in de Oro and the mafioso. Corvini has to stay alive and you can't touch the money until you get your share at the station.
You can however put the money bag into the trunk and keep it as a souvenir
edit: better to do as Ras said, just leaving the bag on the floor is enough, I tried to keep it as a souvenir but then noticed new bugs appearing with the barkeepers...