@Andreas MirzaThanks again and I know you as well as the other posters have been gently (most) leading me to the same conclusion.

Try to identify the smell... grease, pungent food odor, mold/moisture, tobacco/other smoke, plastic off-gassing, paint off-gassing, pet smell, rodent odor, etc.

You can get a moisture alarm that will go off when a sump pump fails.

I gently remind the applicant that we are looking at a 2BR/1BA house and ask if they really want to live in such a small place. 

For tenants that are in place and who are paying and not causing problems or damage, I suggest you make a gentle transition, so you don't lose them. 

Do some reading on basic HVAC design and you will learn that a larger system doesnt work better due to the fact that is does not run long enough to adequately cool the air and remove the moisture that makes you feel hot.

In order for mold to grow, water and/or moisture must be present.

I'm the owner and no maintenance man or PM will ever do as good of a job as me (unless of course you're talking about gas appliances, electrical and permitted plumbing work- all a different story)If it were my property here is how I would prioritize: A bathroom vent fan that doesn't work, -all moisture should be dealt with accordingly, fix it first.Also, they broke the skylight lens when attempting to clean it...

I have an older 70+ gentle man and younger 50+wife renting my house.  

Or, get one of those zip ties that has the screw loop in the head, put the zip tie around the drain hose (gently), and run a screw through the loop into the cabinet.