In single player, When you enter the red portal to Tristram, fight through the enemies and you should find Wirt's Corpse. If you click on his corpse close to 300 gold will pop out and a weapon, Wirt's Leg. Every time you die, you can return to his body and take the gold. However, Wirt's Leg is a special item, you cannot have two of them and therefore can only take the gold.