New member, questions

[Treven Jennice]

Hello, new here and have some questions for you all.

I'm looking to get into multi family homes / duplex housing landlord, or to actively live in one side and have a roommate for the other side. 

I have a lot of questions, but for now I am just wondering why if a place is new or renovated and doing semi well, turning a profit, why sell it, the place I was looking at http://www.trulia.com/property/3072347805-2241-Ham... It seems decent, probably oblivious to what needs done and can't see many photos...just started looking more into this stuff but always been interested. What's best practice to deem if a price is good and how do you take over a property like this.