Feature of Merchant Accounts:

Merchants can freely trade any of their items with the other players. The only downside being that they are not protected by the Forbidden Sale System, and have to be responsible for the security of their account and items.

Change your existing account to a Merchant:

You can find the Merchant Clerk in the Market, to apply to be a Merchant. There is a processing period, where the Merchant's Guild will review you application, and then in 5 days you will receive your Merchant status! If you change your mind, you can talk to the Merchant Clerk at any time, and renounce your Merchant status.

Note: All the characters under level 30 can now directly apply to be a Merchant, without going through 5 days of  verification.

Note: Once become a merchant, you agree that: all of your equipment and items are no longer protected by the Forbidden Sale System, and is not responsible for any loss related to the theft of your account or items held in it. After cancelling the "Merchant account", your character will return to a normal account, and once again be protected against losses that may result from the account being hacked.