Just pointing something out, not saying you're doing this:

6. No scamming of items or account information. Players found scamming others will be jailed and/or banned. Hackers, phishers, password scammers, etc. will be banned.

and
10. Character selling is forbidden, while account sharing is merely unsupported.
...staff is unable to provide support for account sharing. If betrayed when sharing accounts, there is no recourse. We recommend that you never share your account.

So... basically if the account is shared for you to quest for them, the staff cant do anything if you take all their items, other than possibly ban your account.

I'm assuming you are just trying to get cash, but this will put you and other players in danger =\ not the best idea.