If I am understanding you correctly, individual user accounts are set to advance, and if a user does not have enough money in their personal account they have the option to release the job by printing to a cost center. If this is the case - specifically that the billing option for all individual user accounts is set to Advance instead of Arrears, then your scenario is spot on. Keep in mind that if what you are referring to as a Cost Center is actually configured as a Grant, then unlike a Cost Center there is the potential to hit a credit limit either at the user quota level (if set) or at the total amount of the Grant.
Steven, that is pretty much how I figured it.
The one thing my customers can't do at the Ricoh iMFP is authenticate, select a $0 balance personal account, be rejected for output, then change accounts without having to authenticate again. This means they have to log out and re-authenticate, then select thei cost center (we only use grants, but only a few are limited).
Thanks for for the confirmation.