If you've got the ability I'd split the difference (no pun intended) and go with mini-splits.

We added two mini-splits to the garage conversion so we could rent out both sides to separate tenants What was the outcome?

I can't tell if that's a mini closet under a staircase, but if it isn't then that could free up some valuable space in a small dining area.If you're rehabbing anyway, then getting the layout change done in one fell swoop would cut down on overall expenses, increase the ARV and add extra rent ($500/mo in total?)

Mini ponies coming soon...

Closing on a duplex in a few weeks and have been mulling over the idea of replacing the existing window units with Ductless mini splits.  

I got a sweet deal calculator from his services several years ago and it is my mini-bible in this kind of decision.My personal thought is if it cash flows, even low, then I like equity.   

Jingru, I know quite a few successful people down here in south Florida (from local meetups) , also I'm part of M1 Tribe,( is kind of like a mini Gobundace and you meet tons of experts from different industries throughout the USA .) 

My goal is to eventually hire an employee (a mini-me) to take over once there are other things for me to do with my time.

I guess the long and short of it is that PPC can pay off if you know what you're doing.I'm on Perry Marshall's mailing list and I found his free mini-course pretty good.http://www.perrymarshall.com/google/Also, a place called Google Adwords Made Easy(not an affiliate link) has a free ebook about adwords.

Another option would be leaving the existing system and installing ductless mini splits for each floor.