How do I separate my suited houses heat and AC?

[Amadeus Hladun]

Hello everyone, I just have a question regarding my suited property. Both of the units are on 1 duct plan and I want to know if it is at all viable to split that up and install another furnace and AC? 

I would be deal hunting for lightly used furnace and AC units so it wouldn't be much of an issue but the one thing I don't know about is how much of a nightmare it would be to install new ducts or manipulate current ducts and how much it would cost?

Thanks in advance!