You don't have to register for a new set of books or account, Mintbiz. Let me share a few pieces of information.
 

Once you're added as an accountant by your client, you can access your QuickBooks Online Accountant account. From there, you can manage your own books. 

Let your clients add you as the accountant first. This way, you can do your own books.

Get back to us if you have more questions. We'll be right here to address them. Take care!