So @
secplus it sounds like you want access control that is linked to some sorta billing platform. I promise I'm not trying to over complicate this. There are several membership programs out there however based on what your stating you need the following. Also I'm not sure why you referred to the POS - Point of Sale as a "text-overlay device", thats not exactly what a POS is. POS devices can do 90% of what you want here, expect the access control portion.
1. Access control that allows a user in and out of a secure building.
2. Access cards are only active if dues are paid - without paid dues the user can't access the building
3. The monitor in the bar area will show when cards are scanned and if they are current, late, or past due - however if they are late or past due wouldn't that not all them access to the building?
4. When a user pays how/who updates the system?
I've seen solutions to portions of this scenario however I haven't seen a combination solution.