Underground storage tanks, chemical seepage into the ground, etc...

Termador is the best chemical to treat termites in accessible areas but again, you need a branch II pest control license for that.

I know you would want a professional pool company to maintain it in case someone claimed your chemicals, or lack there of, made them sick.

As for the septic that could cause unique proportys in a rental, if your tennent doesnt know better they could really mess it up flushing things that dont degrade or kill the bacteria in the system by dumping household chemicals down the drain. 

There is chemical use that you need to be aware of and maintain compliance.

I ended up having to hire my own exterminator who would come and do a chemical spray every two weeks. 

There are different ways to "abate" lead: replacement (completely replacing any surfaces with LBP); enclosure (lead paint is covered with a wall covering like wall paper); removal (sanding and chemically removing the LBP from surfaces) and encapsulation (covering the LBP surfaces with a special chemical). 

One of my pharmaceutical companies is developing an antidote to nerve-agent exposure to protect the US military from chemical weapon attacks, which shows that I'm always looking for opportunities to create value in places that others have overlooked. 

Do not encourage anyone in the buildings infested, your units or otherwise, to use 'foggers' because while they may work, what they generally do is spread the issue.I'm relatively new to the forums here, so i don't know if it's allowed to say so in a post...but if you'd like to send me a private message i can tell you the chemicals i used (which are available through the worlds largest online retailer......) and, at least in Michigan, do not required any sort of license to use. 

These are non repellent barrier treatments and the primary treatment is done by trenching around the foundation and pouring in the mixture of chemical.