You can buy and sell items with your friends through the 'Market Stand.'

Selling Items through the Market Stand:

Install the 'Market Stand,' which is available through quests.

Set the quantity and price of the item you want to sell.

Upon the sale of the registered item, payment in gold will be made after deducting a 10% commission from the total sales amount. 

If you decide to unregister an item that hasn't been sold, a 5% commission will be deducted from the registered sales amount.

Buying Items through the Market Stand:

Click on Buy' tab in the Market Stand and search for items by name. 

You can purchase items that your friends have listed on the Market Stand.

Note that you cannot buy individual items from a registered bundle on the Market Stand. Check the unit price and quantity carefully before making a purchase.