Here's the idea, please tell me if Batch Create or another plugin can do it:
-have a list of users
-keep accounting records in QuickBooks (obviously not synced to WordPress)
-export users' records and their current balance due once per week/month
-then, instead of calling for their balance, they could just login to their account and see one of their profile or other fields that says Current Balance: $xxx.xx
Again, this is for updating existing WP users, not one-time creating new users.