I bought my neighbours house in order to get rid of problem neighbours and i've put a lot (too much) money into the house.

Then you might be able to privately purchase the other side of the duplex in the future should your neighbour want to sell.

My Papoo fled Greece during WWII and started life in America, getting rich with real estate.

When you combine that with uncertainty in the currency markets i.e. the whole issue of the debt ceiling the problems with Greece, Spain and Portugal commodites have become a "Safe Haven" as well as their normal roles in industry and agriculture.

The neighbours on both sides have recently subdivided and sold off almost all their lots.

That domino was Greece.  

Is the neighbour going to pay for the alterations to your building necessary to enable your building to continue to operate (i.e. meet daylighting and egress requirements) and her/his building to exist on the lot-line?

Look for vacant homes, talk to the neighbours.

Since the comparable sales in the neighbour hood are going for 180-190k, I am thinking of offering for 120k, I could definitely try to sell it for 180k. which means I can probably flip it and make around 25 to 30k in profit, which would also be equity if I keep the house.  

When I responded and told him it keeps the neighbours 14yr-old from taking over telephony exchanges {a gross generalization} that was all he, and most of the room, needed/wanted to hear.As you point out, these folks are experts in their own right ... and a presentation on a real-estate property should be more readily accessible.