They make a chemical that will help remove it not always a complete fix. 

At this location they also had a lot of screws/nails and a lot of light bulbs and lawn care chemicals.

WIth scale you almost always need hundreds of thousands of dollars of equipment, pesticides and chemicals that damage soil and output over time.

I am looking for a contractor who understands building a house with environmentally, non toxic, chemical free materials.

From https://www.nachi.org/ozone-generator-hazards.htmHealth ConsiderationsUnfortunately, the same chemical properties that allow ozone to alter organic material in household air also give it the ability to react with organic material inside the human body.

I don't want to use chemicals because tenants have kids that play there, and I also don't want to breathe it myself.

These chemicals and pesticides leach into our soils and water along with drifting over in the air for miles. 

there are brokers who specialize in selling these google themalthough I have looked at it and owned parks that had both.one thing to keep in mind and this is state specific  though is RVs are much tougher on sewer systems with all the chemicals that go into their sewage tanks. 

It leaves behind dangerous chemical compounds that can cause health issues for people .

yup check zoning first and foremost..one issue is the waste from RV's has many more chemicals. so for a private system this needs to be accounted for and for city sewer they may have something to say as well.but tiny homes usually can fill up pretty good