Need some help analyzing a deal

[Daniel Highsmith]

Found a duplex and need some help with the numbers. I've been looking for deals on single and multi-family houses but i can't get the numbers to work right on any of them. At least i'm learning, right :) Am I overestimating the expenses? It seems like each property i try to run numbers for, the property can't cover the mortgage after expenses are taken out. What am i doing wrong? Any help is much appreciated.

Duplex purchase price is $140,000 which is not what i would pay for it. 

Unit 1 (2bd/1ba) - Rents for $700/mo

Unit 2 (2bd/1ba) - Rents for $600/mo