You will have to first notify the tenants' case manager at their local housing authority who will likely want to dig into why you don't want to renew - in which case like others have mentioned, it's a good time to lawyer up and/or document every instance of them breaking lease guidelines. 

It looked to me like the Termidor application would dig up the drip line.

I'd also talk to your uncle to see if he paid for any of the digging of the well or had anything in writing. 

If you decide to entertain this, due diligence will involve digging deep into the business financials to understand cashflow, solvency, and liquidity, his personal finances, and searching for any liens or UCCs in place. 

I was digging around this forum for a region specific category but didn't find one yet?

A PS the utilities were already ran when I bought the house + the day zoning was called was when I was digging for the patio.

If they wanted to dig into it and see the actual documents it would be costly, since the document is private and protected by attorney-client privilege.Asset protection is a bottomless rabbit hole.

Let's dig into some of the other numbers as well to ensure you have an underwrite that is conservative so that you have "all your bases covered" in terms of risk. 

I have done many where we dig around the entire house, and seal, 15k MAX.

"The Book on Rental Property Investing" digs into renting houses out.