:mrgreen: According to my maintenance guy they are going to get a new air conditioner this summer, because he feels that my current unit is about to die.

Also keep in mind that major expenses will happen eventually like a roof or air conditioner.

I assume  you're referring to central AC, and not just window air conditioners?  

Just make sure to set it aside big chunk of money so when a roof or air conditioner needs to be replaced you have the $5,000 to $10,000 to do that.

I design and manufacture air conditioner cages.

If you don’t have these kinds of funds available, how do you expect to fix an air conditioner when it breaks or solve a leaky roof issue, or pay the plumber that comes out at 2 in the morning on a Saturday night to stop the flood in your basement?

Cost $7k.2) The central air conditioner and furnace are original.

I have seen that for Floor coverings and wall air conditioners but other items could be in that category. 

"Heat pump" air conditioners provide more consistent cool temperatures throughout the house and remove a lot of the humidity in addition.  

It should be as simple as calling them up and asking to add on another meter.I would keep it as a triplex and install a window air conditioner in the other unit.