When playing with a friend or friends.. anytime you want more of something simply give everything that you want cloned to one character that includes money. Then have them save their character in a seperate slot on your harddrive. Then have them give you everything back. Then just simply have them go to the menu and select leave party. Once they do all unsaved information will be lost including giving away that item(s). When they press start to join in and load character they will come back with everything they gave away. Repeated use will give you massive amounts of everything.
even potions to level your character up quickly.