You can set the filters to 3 bed/2 bath and then look at each individual unit.

You may have already considered this, but you might want to keep the water/sewer bill in your name.

I'm not sure how conservative or frugal you are but some of the water and electrical usage by my tenants are astounding, and I am so so glad I am not responsible for their utility bills. 

Everything in the unit (floor to ceiling) was wiped down with vinegar/water and then I shocked the entire unit using an Ozone Generator. 

A flooded basement with just 1 inch of water is enough to cause a lot of destruction.

Ice water is on the house.I'm a regular attendant at Johnson's meetup for a good reason.

They will be very anxious to work with you so you might have to filter through some sales pitches to get to the truth.  

Install new water heater.

So I am looking at a duplex that got water/mold damage on one side, and minor water damage (Door left open or something like that) on the other side.

I live in FL so I know about having to use A\C year round.As you know people mention a brand and price but not model which will ultimately determine the total cost.I was in the exact same situation and due to the rusted coil tubing, and overall condition of the Air Handler decided for a total A\C replacement.Payne is considered "Builders Grade" lowest grade and some A\C guys argue not to install them because it reflects on their reputation when you have problems with the system.Look for the highest seer rated, quietest, best warranty HVAC that is fairly priced.The installer is a HUGE part of the HVAC's life span, along with your regular changing filters, cleaning coils when needed, cleaning drain lines and vacuuming dust out of the Air Handler Cabinet.