Dual climate zone, no heat. 2012 2500 Laramie

[Jason P]

Hello, I'm looking at purchasing a REALLY clean 2012 2500 Laramie 6.7 this weekend but found that no heat comes out the vents. The heater core is def not plugged up, heat in and out, but nothing when I switch from AC to heat. I tried switching with the fan on low before going from cold to hot and same thing. its not that its luke warm or kind of warm, but zero heat at all out of driver or passenger sides, and that's with the dual climate zone synched or running different temps driver to passenger. I can't imagine both actuators going out but I also don't know the history of the truck. Same for the flappers but who knows. I assume that there are 2 flappers for either side correct? Maybe this is a controller issue or is that a pipe dream?

Thanks in advance.
Jason