First rental property purchase, owner check no rep.

[Shay Coleman]

Got a tip in the Charlotte area of the only duplex in a C+ to B Area, where there are VERY few duplexes. homes built in the early 80s and the owner has done very little updating, so it would need at least a cosmetic update.  Each side is a 3br 1.5 bath, and a giant back yard.    they're asking for 315k which isn't doable and it's currently unrentable and the one occupant is only paying 850, when the rents in the area are going for 1200-1600 for 2-3brs.  

I'm a builder and the roof looks like it's got 7 years left, don't know whats behind the walls. but seems too good to be true, obviously need to get an inspection on the other big ticket items, but one side renting at 1400 pays the mortgage.

any advice on whether this looks too good to be true, based on my numbers the ROI is going to be 16% once updates are done and rented.