The property is a 3 unit. each unit is rented for $900 a month which = ~$2700 of rent money, with tenants paying the utilities(Heat/AC etc.)

To get the most efficiency and comfort out of your HVAC system, it should be sized according to your heating and cooling loads.

You mention some work needed....look and make sure to know about the high cost items in a flip...like, plumbing, electrical, and cental A/C Heat and yes...roofing and or siding.

The BP Oil Spill effected everyone from LA to FL, although here in Port St Lucie and the rest of the East Coast we were not effected at all and it did not hinder the purchases being made in my area, Orlando-Miami.

I don't want to "insite" (the dictionary is your friend) a heated argument, but you are making all kinds of crazy claims about random topics.

Also the heating unit is one.

Summers are just as brutal with 100-105 common and heat indexes of 110 plus.

High heat, steam, or UV lights seem the most effective if the place is occupied.

You should be able to get away with dual rapid recovery 40s or 50s which are waaaayyyy cheaper and easier to work with.Have you thought about putting in in-unit heat in the form of 90% furnaces or electric baseboard heat?

It has one boiler in the basement that heats 1st floor and the 2nd floor.