Duplex listed at 150K with potential appraisal of 195K

[Chris Penny]

I am looking at a duplex 6 beds 5 baths total, listed price is $150K. The house is built in 1971, in a B neighborhood, currently rented both sides for $850 each. Looks like the cost for rehab is minimum, sure I need to dig more on this. Given the young age and the rent, what do you think about this deal? 

One key factor here is that the seller just recently sold an exactly same duplex nearby for 150K (so he's pretty firm on the price of this one) and he said it was appraised to $195K. It this applies to the property I am looking at, I can basically pull out all my cash after a few months. However, I am a little bit confused with appraisal here because I thought appraisal value is based on the sold price of nearby similar houses. If that is the case, and given the other house sold for 150K, how can this property be appraised to 195K as expected?