Rent covers a lot of different expenses that new LL's don't see going in, then try to recoup from tenants. 

The roof, appliances, driveway, etc. will need to be replaced in time, and the CapEx is used to estimate those long-term replacement costs.  

Is the home owners insurance covering the cost?  

What if it needs a new roof but inside if mostly ok?

I assume it's just the bigger stuff and single family homes (electrical, roofing, etc) but just want to make sure as I want everything done the right way (not always common here in Miami.)

After buying the property and viewing it I quickly realized why noone had rented either of the vacant units: both units had what looked to be mouse crap on the floor and the other unit had a broken window (not cracked - a literal hole in the glass) and there was a hole punched in the drywall (covered using cardboard). 

*HOAs usually cover lawn care, sprinklers, lawn watering, siding and exterior care, insurance, and more                *This covers most of the exterior line items that you would otherwise have to address in a single family home.

How old is the home- are you incorporating longer term rehabs- like roof, plumbing, windows, electrical and Heating/ & AC?  

Check on the foundation, roof, plumbing, and electrical.

Replace a roof and you will most-likely have zero profit for the year in actual dollars.