The city offers a special program in which property owners share half the cost of sidewalk replacement. Owners pay $3/square foot for sidewalk replacement. This is well below amounts typically charged by contractors.
I recently signed up for the program for our 4-unit building through our Alderman's office. Once signed up, a contractor is sent to measure the sidewalk to be replaced and an invoice is sent to the building. Payment must be made within 60 days or the property will be dropped from the list. The program is offered annually on a first-come, first-served basis and generally fills up quickly. If you are dropped from the list, you will need to reapply in the following year.
For more information and to apply, see the city's of Chicago's website or contact your Alderman's office.