University Life Barista Bar + NRaas Register

I just tried this out in a test game. A barista attendant isn't assigned automatically when you place the bar on a residential lot so you don't need to disable the assignment with Register. However, you can assign one with Register if you wish. The sim showed up and tended the bar. I didn't play long; I don't know if the sim will tend the bar 24/7 or not.

I also don't see the purpose for normal play, but I guess it would be useful for a party.