best heating and cooling system for fourplex in Cincinnati

[Ben Gammon]

Hey Guys N Gals! 

I have a fourplex (2 one beds, 2 two beds, w/separate gas/electric meters) in Northside Cincinnati, OH. I am rehabbing them to be higher end. What is a cost effective way to provide heating and cooling for these units that isn't too low end? I'm leaning towards mini split ductless heat pumps but they are expensive upfront and may not provide enough heat in the winter time. Ideally, I'd like to have the residents pay for the heating and cooling. 

THANKS for your responses!