It's hard to believe that no one noticed this problem before the deed was transferred from the lender to the new owner. Even when buying an foreclosure there is the opportunity for a home inspection. Sure the home inspector is looking at the major mechanical systems in the house but if the house has been sitting empty for a period of time they are likely going to notice a few other things as well.
In this case the other thing seems to be hundreds if not thousands of garter snakes. I'm not sure, if the snakes are as prevalent as the video portrays, how anyone coming to the house could have missed them. Though Caveat Emptor or "Let the Buyer Beware" is the standard phrase used in Virginia I'd say you need to Google the house address and see if there might be a reason the neighbors shy away from coming to visit.
If you are a buyer just starting on your home search in Northern Virginia give me a Cindy Jones and CJ Realty Group a call at 703-346-2213. We have a great home inspector who won't overlook the snakes crawling around in the attic, basement and yard. We'll help you do your due diligence so you don't end up with a slithering nightmare as your new home.