Authoritative Chicago zoning advice

[Christopher Grannen]

Obviously Chicago has a lot of zoning/permit types of hoops to jump through if you exist inside the city limits.  I have been doing my best to research a lot on my own to find out what sorts of regulations apply to my own situation, but a lot of the times, it's difficult to sift through the source material, which is all heavy legal jargon.

Case in point:  Our property has a detached garage on the back of our lot, exiting onto the alley.  The garage takes up 12 of the 25' lot width.  I'd like to use the garage for things besides parking a car, and the idea was to park the car next to the garage, on our lot.  Eventually, pour a proper concrete parking pad (12'x20'), but in the short term, maybe just pour an inch of gravel.  

A friend of mine told me that the City specifies that you cannot park vehicles on your property.  This wouldn't surprise me.  I found this Chicago Driveway Regulations on the city website, but cannot get an authoritative answer from reading it.  I have been in contact with the Alderwoman's office, but I am refraining from sharing any specific intentions or plans that I may have, to stay on the safe side.

MY QUESTION: Is there a recommended impartial source for this sort of city zoning interpretation/information?