Convo got heated, I told him he needed to get his sh$t together and meet the existing deadline which was like 5 days out, or game over.

You really dont want to be in a situation where an a/c goes out on a tenant and what are you going to tell them in the Houston heat and humidity, "I cant fix your a/c because I dont have any money".You have to cut your everyday expenses or increase your income to get some reserves.  

But if you're paying for heat then it could easily be 60% (meaning your EBITDA is 40%).

The chief reason that I don't like it is that it does not account for expenses, like high taxes, owner paying high utilities like heat, and electric. 

An upgrade from window units that are potentially less expensive than central air are ductless heat pumps.  

I purchased this single family home in North Miami Beach, FL five years ago for $120K (Cash no Mortgage) and immediately rented it to the previous owner for $1,500 per month (Aproximatley 10% return per year in cashflow).

Does anyone know how many BTU's it takes for the whole Northeast heating season per square foot of building?

The house would need pretty extensive upgrades -  I would need to replace entire HVAC system (including converting from oil heat to gas) and it would most likely need roof and siding. 

I understand that municipal/court registrars will store mortgage related data (I have seen this for Miami-Dade county).

Can't take the heat?