There are three methods for trading other users in the game.
1. Auction House
The Auction House is a player-run market for players to list their items for sale. Players are able to bid for items or instantly buy-out an item, if the seller has set this option. There is a 10% fee to list an item.
Escrow is the safest method for transferring something to another user, as both participants are required to enter their password and confirm the escrow agreement.
The bank is the simplest method for transferring cash from one user to another. It also provides investments for a nice profit. There is a 5% tax deduction on all transfers.