Only 7,500 in rehab (paint, fix hardwood, minor heating, and a fridge) and it is now worth approx 135,000 & rents for 1380/month no utilities included.

Doing a studio would definitely improve heating/cooling as I could put in a ductless mini split and it would work well for the entire area.

Then hubby and his workman were in the property 12-16 hrs/day, working on the first floor in the dark, until they got water, gas, electric ready to go on, so heat, light, a working bathroom. 

It dawned on me that I do not have any recommendations for an inspector in the Miami area that is experienced working with investors and would have my best interests in mind.

I'm not sure about elsewhere, but in North Carolina, air conditioning is not required at all, provided the residence has window screens, so there are no true emergencies for A/C like there would be for no heat. 

I live in the main level unit which has Central AC/Forced Air heat.

I don't think adding another element to the arrangement that could potentially cause disputes is smart and I haven't had anyone abuse the heat/AC over the several years I've done this so I plan to keep it that way. 

The house had central heating but not AC.  

Having access to the MLS, running comps and understanding the Miami market will give you an upper hand. 

Current new tenants have a dog that they chain outside, in the worst damaged area, and in the heat, which I have given up on trying to repair, and when they move I will install a nice stone arrangement, perhaps with a small crabapple.