What could be wrong with his deal?

[Joel Wilson]

Hello, i would greatly appreciate any feedback. I am new to analyzing deals, and i have calculated this property ( http://www.loopnet.com/Listing/19964090/1215-and-1... ) as getting a cash on cash ROI of 20% with a downpayment of 25% - $455000. Accounting for mortage ($6619/month), pm at 8%, CAP EX & Vacancy at 5%, Insurance at $500, taxes at $1895 (all per month), this property is cash flowing at $7950/month. On paper it looks like a great deal in this current market. My question is: what could be a reason that it has been on the market for a while and that no one has bought it yet? Could it be a bad inspection? Any list of ideas would be greatly appreciated for a guy learning. Also, if you believe i am calculating wrong on paper, please let me know!

Thanks,

Joel