If you do see some signs of "M" or mildew it is at a minimum a sign of trapped moisture.  

The biggest being that they usually destroy the window and the moisture causes mold.

It has great information on Mold Basics, Mold Cleanup, Moisture and Mold Prevention, etc.  

.• Metro areas which do not experience hard freezes or significant moisture.

Now, let's tackle it like a pro: Identify the moisture source causing the mold, fix it to prevent a comeback.

Mold likes moisture.

Then we add an addendum for other things.... such as 8 pages property rules, 2 pages property condition report (move-in inspection list), 1 page mold/moisture information & disclosure, 1 page lead based paint information & disclosure, 1 page no-smoking policy, 1 page pet agreement, 1 page service animal agreement, 1 page "other", etc.I schedule 2 hours with new tenants for the move-in.

This will be the first building we put up, so the Electrician, plumber, security, etc can start putting their main switches and boxes in the office.The next two small buildings they have poured the footings and now have: a. placed rock grit on the ground, b. put plastic moisture barrier down, c. laid rebar across.

We've found them coated in mold, nicotine & what appears to be petri dish science experiments as moisture dwells in the lower trays.

One contractor said moisture is coming through a hole in the exterior stucco, but another said no way because the vapor barrier would block it. 1st one recommended installing insulation, but I've also read this can increase condensation problems.