4 unit section 8 rental- Best solution for heating and AC?

Hi all,

Going to start rehabbing a 4 unit rental property in DC soon, and wanted to get opinions on the best route to go with heating and AC. It is a 4 unit building- about 4,900 sq ft- each unit is 3BR/1BA. Currently there is no central HVAC system or any ductwork.

I've thought about:
1) the ductless HVAC systems- supposed to be about $500-$900 per 400sq ft that you are heating or cooling
2) the hotel/motel style PTAC wall heating/cooling units that run about $1,000 each

Any thoughts or experiences? The limitation is that the Section 8 check-list says 'every room used for living must have an adequate heat source.' The concern there is that if i got the hotel/motel PTAC route I'll need to have 5 or 6 in each unit...

Would appreciate any thoughts. Thanks