Having had similar experiences in the past, I will add the glaring "red flag" that is visible to me.

I’m in the red hot market of CT and just went under contract today for a duplex near a college.

I will look at all of these and take some deep dives.

@Chris Boyd, no deep analysis needed IMO.

This is where you put on your detective hat and dive deep into the world of real estate data, demographics, and trends. 

I bought with a cash-flow on day-1 and could tolerate two vacancies before creating red-ink, so it's crazy to be penny-wise and vacancy foolish.I know there are those here on BP that harp on hobby vs professional business operations, but there's more to the bottom line than just GSI - - consider the opportunity losses created by vacancies.

In a climatic health resort area deep in the Bavarian Forest, where the air is clean, there is plenty of nature and real estate is affordable. 

Any red flags?

So if someone bought it at the tax sale and then didn't want it and didn't pay the tax on it, that is a big red flag that they may have found something wrong with the property and decided to let it go.I would do some research on what you bought.

I definitely need to stop this in it's tracks so the smell doesn't TOTALLY infuse the place@Bjorn Ahlblad  I guffawed when I red your reply!