Septic tanks, even though they're full of crap (no pun intended), are sensitive things - the bacteria are highly susceptible to overload, bacteria soaps, bleach, chemicals, and other stuff that simply won't break down or will kill off the bacterial load.

I have allergies (the main reasoning for removing the old carpeting) and didn't want to deal with potential chemical fumes.

The particular house ended up being EFIS (synthetic stucco).

Like every plant it is easy to kill with chemicals and it can not grow without water. 12k seems very expensive for spray & paint; except if you had to rip our drywall and wet insulation etc..Also, your inspector should have questioned the absence of a floor drain - at least here in Milwaukee every house has one and if you can't find it, you know it's been floored over.

A product called "Nature's Miracle" (you can get at any pet supply store) will break down all chemicals in animal urine but, if it got through the pad and on the sub floor, I would definately replace and not allow pets anymore.Ever smelled a home in the summer with soiled carpets????

Work as a chemical engineer but participate in RE investing. 

Yo want no regulation or industry standards for the STR's, you're ok with this because it works for you, imagine now if the Natural Stone Institute had no standards or regulations for the countertops you're installing in your units and now you're emitting toxic chemicals for all of your guest, then take this scenario onto the plumbing pipes, now look at the flooring requirements, If everyone who has some sort of profit benefit in your Asset took the same position and wanted no government oversight or regulation in the name of individual tunneled vision profit, we'll be back where we were in the 60 and 70 with mass numbers dying from asbestos and lead poisoning all from renting your units.   

I have been told by the local pest company, that the chemicals that they will be using, is harmless to kids and pets.

In fact, Indy is the ONLY U.S. metropolitan area to have specialized employment concentrations in all five bioscience sectors: agricultural feedstock and chemicals; bioscience-related distribution; drugs and pharmaceuticals; medical devices and equipment; and research, testing, and medical laboratories.Population Growth: With a metro area of over 2.1 million people, Indianapolis is the 2nd largest city in the Midwest and 14th largest in the U.S.

Growing up poor the richest person I knew was an engineer at a local chemical plant making $50,000 a year.