Oahu, and the rental is in Diamond Head, on a unique street above Kapiolani  Park. 

Here's a perfect example of what I mean by "cookie cutter flip" (and I forgot to mention the Jeld Weld hollow core Home Depot doors).http://www.recolorado.com/homes-for-sale/1385-S-Raritan-Street-Denver-CO-80223-202634396

He was paying a guy across the street $75/month to shovel snow, mow the lawn, and pick up trash around the building.

I can't buy down the street but that similar property has appreciated as well.  

The buyer the property manager has brought owns another duplex on the same street and the manager also manages property for that owner and would then continue to manage the same property and so would get a commission without interrupting the property management fees.

I'd maybe talk to the  neighbors on the street and ask them if its ever happened to them.  

Shahla Tehrani just call the city's street department, traffic engineering department, or transportation department.

Personally I do not have much faith in paper assets/Wall Street.

The other 10% will require more due diligence and know how (e.g. a vacant property in the middle of the woods with no street address and a deed from 100 years ago). 

All if you might like to know that I walked across the street and found the railing in the neighbors yard!