I wake up every morning and check the MLS, county auditor's website, REO listings, auction listings, etc.

You can use the auditor, know what land codes you want (duplexes are 520, triplexes are 530, 4-19 units are 401), pull the list so that it will be in an excel file, take that file and move it into a dialer system, start cold calling.

The other way is to use the tax estimator on the auditors site: https://apps.franklincountyaud... 

The city requires you to register your rental with the auditor, that way they know who you are and can enforce the rules on you. 

I've checked the property auditor, googled the owner(s).

We buy very few properties that are what I call "struck off" they are literally stricken off the tax auditors books for non pmt of taxes. some of these have been off teh market for up to 4 years and not to many of them are worth anything.

One thing I noticed is that most of the valuations for properties on the auditors website are about 60-80% of their real market value.  

The counties I am most familiar with, Franklin (Columbus) and those counties that surround Franklin, have zoning laws and land use codes and, if the property is in a subdivision, many of those have restrictions as well.Find some Columbus SF addresses on Zillow and look them up on the Franklin County Auditor website. 

@Dave Dunaway as long as the units meet code, you're good...we just passed on 8 duplexes where the design called for basement apartments...typically, below grade footage carries less value than above grade...so, for example...if the upstairs is $100/sq.ft. you won't double your square footage at the same rate by putting living space in the basement....and you are basically asking the auditor to reassess your taxes based on the square footage...so you claim it...you pay taxes on it.Most of the other inherent issues are around controlling water...the right thing to do would be to install a perimeter drain and sump...if there is any moisture or water intrusion in the basement (and there will be), you run the risk of mold inside the finished walls...I think my ultimate questions is who would really want to rent an apartment with the bedroom in the basement...even if it is finished, but who knows.

I currently work as a full time auditor, and was hoping that I can put in extra hours each week to try to even close one deal, but as you said, it would be a full-time job itself.