Obtain 10 Discarded Supplies.
A big part of making money is shamelessness. You have to be willing to profit off of the misfortune of others. It all ends up boiling down to one question: How much do you love money?
When Marshal and his crew abandoned their refuge up to the north, they left behind lots of supplies. This stuff isn't rare, or even particularly valuable, but it's there if you're willing to take it. His camp is up in the cliffs, to the north.
Oh, and be on the lookout for whatever it was that made them leave...