Install A/C and reinstall furnace in my rental (Denver metro)

[Jesse Park]

I purchased a 6bd/3.5ba home ($450k) in March, put $55k in reno, and I'm house hacking with two roommates. I'm looking to cash out refi next year.

I have a 12 year old furnace with ducting. With the summer season ramping up, 2nd floor is getting upwards of high 80's and I got some quotes for A/C. 

One company quoted me $4800 for A/C only and $6800 for A/C and furnace. That's only $2000 more for the furnace, which seems like a good deal. Upgrading from a single speed, low efficient blower to a variable speed blower also sounds like it will put less load on the system which may also increase the life of my electrical system. Another benefit is that with the new efficient blower, I can recirculate air by just having the fan on without using the A/C to cool down the house.

Question1: Should I even consider investing in an A/C to make tenants happy and raise the value of the home for refi (double benefits)?

Question2: If I do choose to get an A/C, should I also replace my 12 year old furnace (life of a furnace is 15 I believe) to take advantage of the combo deal and to get a heard start before my furnace dies?