Coach house not recognized on zoning certificate

[Phil Janasac]

My fiancee and I are in the process of purchasing a 2-flat with a coach house in the back of the lot on the north side of Chicago. Our lender requested a zoning certificate for the appraisal and discovered there are only 2 dwelling units (from one building) noted on the certificate; which technically makes the coach house illegal even though I was always under the impression that coach houses (outside of zoning law) were considered “legal non-conforming” structures. 

We were planning on renting this coach house out, or possibly living in it ourselves, but now I’m worried about the liability that comes with doing that; our realtor and real estate attorney don’t seem to be concerned at all since they’re pushing us to buy this as a 2-unit property, which would make the legality of the coachhouse irrelevant in a sense. There was a note on the zoning cert that said “DOW 12-3-54 - DEPT RECORDS REFLECT ONE BLDG WITH TWO UNITS” - which I think is from Department of Water. This doesn't give me confidence that we can get the city to recognize a second building, even though a basic inspection would determine so. 

This has been a lot to process. We have been waiting months to get this short sale approved and now we are being hit with the fact that the coach house isn’t legal. Personally, I feel like the sellers, and the listing agent, grossly mis-represented this property by not disclosing this, and justified it because they were selling it as a 2-unit, even though they had rented out this coach house to a family for the last 13 years. 

What can be done to get the city to recognize it as a legal dwelling, or that it even exists? Would we have to get it re-zoned? Is it still worth proceeding with this purchase? The coach house is in decent shape and ready to rent, but we would want to upgrade it in a few years. 

As always, appreciate the thoughts and feedback.