IMO that's a huge red flag that they will be a nightmare. 

Are you talking about the Tower District? 

In monopoly you win with 4 red houses, and a green hotel, but in my experience you need only a single blue apartment building for finacial freedom. 

Seems like a red flag that she is able to pay a year up front.  

So, I'm hoping with some help from some experienced people on here to avoid any major red flags or pitfalls.  

Id be looking at the Orange & Silver line on the west side of DC, and the Red line on the north side of DC.

I understand that could be a red flag because that could mean if they cause damage or something it may be difficult to get money out of them, but wouldn't it be preferable to get your money up front.

The first thing that strikes me as a red flag is that the current owner hasn't even owned it for a year and is looking to sell for a $300k increase on what they paid for it.

This is a red flag for me that I learned the hard way.  

That said, I do agree with others that the cash-flow-versus-appreciation debate is somewhat a red herring.