Duplex and 3 Vacant Lots

[Tom Scott]

A duplex in my small town has popped up in the past few days. The deal includes 5 lots, the existing duplex takes up 1.5 of the those lots possibly leaving the the other .5 of a lot useless though I need to check on that to be sure. 

The duplex, which is 1600 ft^2 total (2- 2/1 units) is supposedly grossing $800 a month total though it is currently vacant. They are asking $160k for the whole package which I think is too high. 

The remaining 3 lots are buildable according to the agent, though I will verify with the county before moving forward. If I could build 3 more duplexes, perhaps 2 story units with a larger floor plan around 1200 ft^2, then I could get around $800 a month for each unit. The Duplex alone is obviously not a money maker at their price point, but I am unsure how to factor in the additional lots. 

Tom