I've not heard of ADU's in Columbus or, for that matter, Ohio. That doesn't mean they don't exist but those that do exist are most likely illegal, at least in most (if not all) Central Ohio counties (and probably the entire state). 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. Those that have 510 as the land use code can only have 1 unit on the parcel. If you ignore the restriction, you have to make the conversion without permits which is dangerous in terms of health and safety and in terms of your financial health - the city can force you to remove the improvements and, in one case I am familiar with, to tear down the entire illegal structure. Also, if you let any person sleep in that illegal setup, if someone is injured or killed within it, it is almost certain your insurance will deny the claim. All in all, I can think of no good reason to try this, though I run across similar at least several times a year.
Though I have great confidence in what I wrote above, it is not necessary to rely on my experience or my self-perceived knowledge. Call a couple of the code enforcement offices in the area and let them tell you what is and is not legal. Not being truly familiar with the concept of ADU's, there is a very small chance that I may be giving you a bum steer.