After I consulted the builder of the apartment, and researched this online, the conclusion was that the mould is coming from humidity inside the house and the lack of air circulation.

Florida can get up to 50% humidity up to 6 months a year, so there is a good chance moisture can build up.Depending on the type of ductwork you have, some materials are more indusive for mold growth.As for the floor, im not sure.

I'm in SFL and the only slow months are September and October mostly because kids are back to school and it's hot and humid as hell here. 

If you install hardwood floors during less-humid months, their moisture content is pretty low.

At least, hold onto your property in CA, so you can come back if you aren't happy in TN.Not only will the weather suck - really humid in summer, icy and cold in winter, but the culture is completely different.  

The unit was reading at 65% humidity. 

And please remember that sometimes it's not just heat but also humidity that makes it unbearable. 

The balto forecast is 90+ 4 of the next 5 days with humidity on top of that.

The hole was caused by an arc fault when one of the electrical conductor broke loose from the wire nut - hot and humid weather in Florida over the years the solid conductor got corroded. 

The black mold is due to too much humidity... are you using the bathroom vent when taking hot/long showers?