Construction Not Finished in Time of Lease

[matrixfan321]

My question involves landlord-tenant law in the State of: Illinois

I recently rented an apartment for lease beginning this Monday. However, the landlord has not completed construction. Thus, we are not allowed to move into our apartment on the lease date. They are offering to put us in another place (farther away from my classes) and in a building much older than our lease. Also, the company offered to take off 50% of rent for our stay at the other apartment.

However, I find this ridiculous. We should not be paying anything at all. Is there any legal ground that I can stand on?

Here is the email:

My name is [redacted] with [redacted] and I would like to touch base with all of you to let you know your current situation with your apartment at [redacted]. You were suppose to be moving into the apartment on 1-18-10 but the city has not given us an occupancy permit due to the wheelchair ramp that was built. The ramp was approved on the blueprints by the city before we had begun construction. So we currently are having to make those changes before we get the permit. The tentative date to receive the permit is 1-25-10.
We are going to put you in a comparable apartment and give you 50% off of the rent with utilities included (for the time you are in the other apartment). I will be showing you two different apartments on Monday and you can pick which one you would like to live in for a week or so. When moving out of the apartment and into [redacted] we have reserved a truck to help you move into your apartment.
I do apologize for the inconvenience. Please let me know if you have any questions.

Also, the date for receiving the permit is tentative, so it is a doubtful promise. What should I do?