You can't just buy a unit in a 2 flat - you can buy a condo in a small condo building but to buy one unit in a 2 flat requires extensive zoning changes, tax pin changes, ect.  

So I need a way to import my full list to a map view (like google maps), and then be able to select just the markers that fall within a few square blocks.   

In my for rent ads, I post a little about my criteria and then ask if they smoke or have any animals. 

I just recently added Someway and VRBO as listing channels but have not yet optimized completely to increase income and to limit time requirement.I would recommend that you calla few property management companies that handle rentals in your area, have them provide furnished rental comps and expenses.  

This is to say that my 4 year investment yielded net 224K, approx. 56k per year...I did a lot of improvement works on the house: new floors on two of the three floors, tore down a wall down, completely rehabbed the basement, added a bathroom, put in a new kitchen, replaced some appliances and many other cosmetic jobs which were costly but I did myself with the help of my father and the occasional local handyman.

The block is mostly houses from the 1950's and listed as 0 bedrooms (no closets?)

The home needs extensive work that includes kitchen and bathroom remodels;  HVAC installation; boiler/baseboard heaters removed; plumbing work; and some girder/sister joints replaced. 

Some older buildings cannot be extensively repairs.

Unfortunately, it has not resulted in the home prices on the surrounding blocks to appreciate in price like how Barclays center did to apartments and houses in Brooklyn. 

Instead of helping me with the sale, I was able to negotiate an added stipend which covered my mortgage.