Let me know if you need any assistance.
The city will not automatically order you to take the property down, you might be able to get a permit for it. Although you will have to take it to code an potentiall pay some fines. But remember that you will not know until you check with the appropriate authorities - I have known some cases where the city have indeed ordered the removal of the addition, and have imposed steep penalties in addition to that.
There are many other things you need to be aware of, and that is only one of them, when making such a big purchase. Make sure your agent is experienced and get you coverd during the entire process. A small overlook of an issue can have very serious consequences.
ABR - Accredited Buyer Representative