It could be almost anything ranging from a weak breaker, a short, high amp pull from the compressor due to dirty condenser coils, high amp pull from the compressor because it is going bad, absence of a 3 or 5 minute relay so the unit cycles to early, etc.

Monthly expensesTaxes 445Insurance 102Mortgage: 1650PMI: 243Repairs: 300Vacancy 150Expected rent 1600 per unit minimum, 1700 is more likelyPurchase price 375,000Downpayment 5%Renovation costs 15000 (new floors/cabinets/appliances in Unit B kitchen)Both furnaces are 17 years old1st water heater-3 years 2nd water heater 7yearsRoof:12 years1st AC condenser 4 years 2nd AC condenser 12 yearsWould appreciate peoples input, I will be living in unit B (House Hacking) First investment in Atlanta. 

Windows will develop condensation when the outside air temperature and indoor air temperatures differ, unless they have good airflow around them.

also you probably bought low end type properties were this type of thing is far more common than you really can imagine.. it was determined by one of my vendors years ago that most of the theft was done by workers of the contractors themselves.. they deliver the goods know exactly what is there come back that night and steal them.Most folks in these type of neighborhoods only install water heaters  HVAC condenser utls literally the day the tenant is moving in.. and if its before that they hire security or someone to sleep in the unit the night before.. welcome to the reality of those areas.

If so then you need pics of the condensers.

this includes inside unit, outside (condenser) unit, and repair of easily accessed ductwork (required by law).  

This can lead to additional corrosion w/in the pipes, possibly leading to premature failure of the heat exchanger, which is not inexpensive to fix as I just fixed one on one of my properties.Assuming you're on gas, you could (imo: should) install a condensing gas boiler.

Steam was fed up the line into the radiator, and then would recondense to condensate and return back down the same pipe via gravity to the condensate station or pump.

-neighborhood is a C+, but in a very desirable school district (HEB ISD)-property was fully renovated in September 2014, but could possibly need new water heater and condenser soon for one unit.

J's book is an excellent place to start because it condenses and focuses a lot of the most important information that's relevant to what you're doing.