NOTE: It hasnt be confirmed by me but others say it is working. Go try it at your own risk.
1) Bun an room at an inn for 5 silver
2) Put a box in the vault and put in there a rare item worth at least 10 gold.
3) Get rid of your ownership of the house and leave the items in your house vault.
4) Go buy a new room in some other part of the same town.
5) Set up vendor mode and the items in the old house are still available to access.
6) Have a second account or player be ready at the broker.
7) Put all your items from the old house for sale at 1 copper.
Start Selling the items and have the other player / account search for you at the broker.
9) Once he has the item up spam the Start/Stop selling button and have him spam his buy from broker button.
10) This will duplicte the item multiple times however becareful they did seem to catch the players that did this.
11) The players did it at the night and didnt get caught but again the next day and they caught them and banned them.
12) Try it at your own risk.