The closed auto plants were also often abandoned in a period before strong environmental regulation, causing the sites to become so-called "brownfields," unattractive to potential replacement businesses because of the pollution hang-over from decades of industrial production.[12] The pattern of the deteriorating city by the mid-1960s was visibly associated with the largely departed auto industry.

Beyond the environmental and safety benefits, one could also take way access to a house if a tenant was no long allowed in.

I'm not an environmental hygienist so anytime there's a question of mold, I have air tests done to confirm if that's truly the case.  

Pre 1978 houses can have code and environmental issues.

@Pavel Sakurets the environmental studies should clearly spell out what needs to be done.

(emphasis added)The World Health Organization and The Environmental Protection Agency aren't "credible" in your humble opinion?

This allows me to cover any major unforseen expenses, for instance a roof replacement or heaven forbid another environmental cleanup.

Commercial appraisals can cost more and the lender may require significantly more due diligence like a phase 1 environmental assessment.

I have my bachelors degree in Environmental Sciences and I'm looking forward to flipping a couple of properties with "green" in mind if it makes sense financially.

I focus on destination type tenants such as barber shops, vet places, regular doctors office, emergency clinics, restaurants, karate schools, fitness centers, environmentally friendly dry cleaners, etc.These are places people HAVE to go to do business.