Extra costs for insulation are offset by reduced costs for HVAC equipment and ductwork. 

(Note the furnace is central heating so no new ductwork should be required).What do you think renters would most notice and value?

Is there ductwork already in the building?

It wasn't just a little rehab - put in CHA unit and all ductwork (it had window units), tore out the 4th bedroom to make it back into a carport (more desirable than extra bedroom), ripped off the walls on the enclosed porch to make it a screened porch again, all new energy star custom windows and doors (got them on a holiday sale at Home Depot so 15 % off and had a 10% off Lowe's coupon that I had HD honor and got 18 months 0% interest) and painted inside and out (Pro Plan paint at HD - another discount and same 18 months financing), new appliances (scratch and dent with 10% off and 18 mo. financing at Lowes), and new countertop and ceiling fans.  

@Lee Gierszewski - on my recent flip to rent property, there was gas forced air with ductwork in place.  

Hello  Mano,      I would think even with temperature in 50's that the second floor would be warmer than 1st floor, did HVAC crew check to make sure the duct work to 2nd floor vents still connected? 

I am a contractor , I just did a complete gut rehab on MY property , I only called my AC sub out for the HVAC , that was 10K for new unit and duct work .

Just got an inspection report back on a SFH in the Midwest and I have some questions.The house is a single level with no basement and a crawl space which houses the ductwork and structural members.The report turned up some standing water in the crawl space as well as some mold on the wood framing.

For a rental adding central AC in south Philly is a must so a house with ductwork in place is a big bonus.

Which will make it much easier in the future to accept when I enforce the lease to the letter on future occurrences.For example, I just paid to have duct work cleaned at a rental property because the tenant was complaining of allergies and possible mold in ducts in an older house - but I didn't have to.