Here, maybe this will be interesting/helpful to you - I am currently working on doing this right now with my own property, which happens to have a nearly identical loan amount as yours, and there is $50,000 in equity I could refi out.

At $22000 annual rent and 55% expenses that gives an NOI of $9,900... nearly identical to Todd's.

One of the units' rents had just been raised to $1100/month, and all units were identical. 

We purchased it in 2012 for 305K and identical homes in the neighborhood have sold for 395-400K in the recent months.  

Tonight, two popped up at about the same time and when I open the listings they are almost identical buildings, owned by the same person, and are each going for $165K.I'm considering making an offer on both duplexes and I was wondering if its an acceptable practice to ask the owner to consider giving me a discount for buying multiple properties from  him.

You can have two identical buildings next to each other with different cap rates.

If identical buildings not encumbered by long term leases are for sale and one is performing to market at $100,000 NOI and the other is mismanaged and only collecting $50,000 NOI AND the market cap rate is 10% then only an idiot would sell the first property for $500,000 while the second would go for $1,000,000. 

My one suggestion is to find your  Investor Identity.

There is a small difference in training maybe - but the end result and the listing database are identical.

You can't exactly compare a fully renovated house with granite counters to a 20 year old house with no updates even if their identical model with same sq. ft. on the same block.