The ABC's Real Estate Investing by Ken McElroy is an excellent book for a basis on underwriting and due diligence.

Your customers have a due diligence requirement and can't just take your word that you're organized as an S Corp. 

Take ownership of your mistake and learn to do the proper due diligence recommended above😊

I would say that you really have to do your due diligence on the team that you are building.

Hopefully you will be booked in advance and won't have many week-end sites available, that depends on how nice the place is and the clients you serve.Your due diligence begins with the area, comp other parks and similar motels as far as gross income.

Because we work primarily with new investors using independent evaluators is due diligence on our part.

I believe the biggest general reason is lack of due diligence.

Sounds like you already closed, do you have any Army Corps issues that came up in your due diligence, i.e. blue line streams? 

Any due diligence you suggest? 

You have to ALWAYS do your due diligence, and get the right people on your team.There is no such thing as "stopping to find more confidence".