I'm a practicing attorney in SE/Central Iowa, practicing mostly in transactional matters, and litigation that stems from the same (read as "matters like real estate transactions, and subsequent eviction for investor purchaser).

With that said, I am not a lawyer and strongly recommend you consult a lawyer to make sure any contact you use does not expose you unduely to litigation and meets state requirements. 

Umbrella is nice if things go to litigation, and in the final analysis isn't that expensive...it might cost you two months worth of profit on one property to protect all your properties.

My preference is that I am less inclined to sell to a civilian because of the increased scrutiny & higher risk of litigation (not worth it to me for a few grand) .

I know I buy more than my fair share.On one policy I bought for a subdivision I was building it was a 10 year liability policy for 1 mil that I paid 30k for.. this to protect against any claims 10 years after I had sold them LOL.. and of course all the subs have insurance and so on and so forth.. basically cost of litigation if I was ever to get sued insurance. 

I was thinking I could work for a residential development company as a civil engineer or something similar.

If they claim to be rightful occupants to the police, then the request names from the police so you can pursue civil eviction.

In the mean time contact builders, developers, county building office, civil engineering firm,etc and see what issues you or a buyer might face.

So if by an off chance i had a tenant that claimed they had a black mold problem that hopitalized the tenant racking up medical bills and rehab costs, then i imagine the insurance company could deny the claim as it is 'enviornmental' leaving the liability up to whomever owns the property....If it was in my personal name then all my personal assets could be locked up in litigation.

I know they are never coming back and they are never going to give me their new address because they then know I can file a civil suit against them for damages (your runners likely know the same thing which is why they didn't provide this for you when you mentioned it).