Upgrading commercial (5+ units) apartments HVAC

[Garth Kukla]

Hello BP family,

My name is Garth and I'm a local wholesaler in the Northern Kentucky/Greater Cincinnati market and I was hoping to get further insight regarding how to best handle separating HVAC in my 7-family.  Currently, I have 2, 22-year-old high-efficiency furnaces that are controlled by 1 thermostat (I pay for the heat) and window units for AC which the tenants pay.  That seems to work out fine though I'll need to make some decisions soon regarding replacing the furnaces with new ones or providing each unit with their own separate HVAC. 

Thankfully there is ductwork throughout and I personally feel that higher-end apartments need there own HVAC.  Obviously, this will be at a cost of about $4k/unit ($28k total) or I could simply keep things as they are and spend $8k to replace the furnaces before next winter? 

Can you provide the pros and cons of both options for me?  Any and all insight would be greatly appreciated and I hope you all are doing well during these trying times,

Garth