Duplex for my first investment property...what am I missing?

[Dallas Bass]

I've been looking into and researching investment properties for a very short time. Just out of curiosity, I looked up some properties that are for sell and found a duplex for $180k. 

Both units (3 room 2 bath each) are currently being rented for $850/month and the tenants pay the utilities.

It's in a decent neighborhood (very low crime) and is about a five minute drive from a division II college. 

As far as I know, it's in pretty good shape too. Of course, I don't know that for sure because I haven't been to the physical location or had an inspection.

I talked to the realtor and she said even though rent is at $850 she thinks that is too low.

Looking at things on the surface, it seems like that is a good deal. Am I missing something obvious?