Buying a duplex that needs certificate of occupancy

[Frank Jennings]

I'm considering purchasing a duplex. It's not a true duplex. What I mean is that it was originally built as a single family home, but now there's a door cut out on the right hand side with stairs up to that door. And in the seller's disclosure it says that a certificate of occupancy will be required by the municipality. My question, is this going to be an issue? The current owner has owned it since 2007, and has never lived in it. So I think it has been a duplex for awhile. Does this mean it's not a legal duplex?