Players may open accounts with player shop facilities like "Be Your Own Boss Mercantiles" in Peltarch.
Accounts vary by location but once you pay for an account it is yours forever whether your goods are being displayed in a stall or not. You can always access your stock at whoever is operating the stalls.
After you have an account with a shop facility, you can choose to put your wares up in one of their stalls if one is available.
Items sold from a shop incur a 10% commission fee. You can retrieve your shop profits from your stall.
If your stall has had low activity in terms of not many wares, not restocking wares or no one is buying your wares, you may be vacated from a stall so that other players have a chance to sell items too.
Transferring items amongst your PCs using player shops can be considered a form of twinking. Please see the Twinking Article for more details.