I'd start with attending anything the National Association of Residential Property Managers is conducting.  

We  actually make our vendors sign a code of conduct form of how they are to operate when dealing with our clients properties.

I review their records and conduct a detailed inspection of the rental prior to renewal.

JayMA is one of 3 or 4 states that pretty much require an attorney to conduct the closing.

An environmental engineering firm can conduct an audit for you and likely answer your question with certainty.

Your title-company or closing-attorney will conduct a title-search on the property to make sure that the seller doesn’t have any liens against it.

Yes, you need to Foreign File in every state where the LLC conducts business :sigh:

After conducting my due diligence, I found that some of these properties which were vacant were in probate court.

The risk is when you are conducting illegal activity, it invites trouble.

Albeit, the total was only about $150 worth of supplies; nevertheless, this could have been a very different scenario, in that, what if it was 10k worth of Drywall, wood, fixtures and appliances; I would have conducted myself very differently.Turns out the dude is like Jesus with table saw and a pile of wood.