Yeah, if they wanted minimum complexity (low upfront cost), it would be a socket tied to the unit, which would work great for those that have assigned parking... or those that are like townhomes and just put a socket on the front/back that the renter can plug into.
For 'festival' parking, without giving the power away (or spread out over all units or all units with plugin vehicles), would require additional complexity. There are charging stations meant for more commercial customers that have fobs to indicate who should be billed...
Like the JuiceBox Pro 32 (I found at this url:
https://evcharging.enelx.com/store/commercial).
$1300 for the unit, have your complex electrician install it (or hire someone to)... I would only put them where I would not have to make long runs for power... or setup an area (the less popular parking spots) if I needed to run power and put the chargers all there.
Charge them a $25 to $50 'setup' fee to deal with managing the system, etc. I would guess that the JuiceBox Pro would allow me to input what I paid for power and how much I want the user to pay... and either have it billed directly to them (site they can pay with an app) or add it to their rent.
But I do not own apartments, so I am just speculating on all this.