First, goto the Imperial City Talos Plaza District. Then, open your map (the one that shows the names of all the buildings in your current location), and find Dorian's house. Go inside his house and bribe him all the money you can, then make him upset by making disposition going down by playing the disposition mini game, and repeat the bribing process. Once you've bribed him a good amount of money, such as 1000 Gold, kill him as fast as you can.
A good way to kill him without allowing him to run away is to push him in the other room and stand in the doorway while attacking him. After he's dead, goto his body and keep clicking on his gold. DO NOT select "Take All" as it will ruin the glitch, just keep clicking his gold. You'll get the amount of gold he has on his body every time you click it, and he will never run out of it.