Legal Question in Landlord & Tenant Law in Illinois

It is unfair. I would question continuing to rent from someone who threw ultimatums at me like that. But that's up to you. In any event, let's say today, 12/10, is the day he said that, and expects you to return it signed on 12/21, and you don't. Even if he immediately gave you a 30 day notice, it wouldn't be effective until 2/1 - because if a rent date intervenes, you go to the next one (although you'd have to argue that before a judge) and so you would have at least a month if not more to find alternate housing, although at a bad time of year.... Also, there's a legal concept called "duress" and contract MAY be voidable if signed under duress. But proving it after you sign it becomes problematic at a future date so I wouldn't rely on the concept if something came up..... But 'illegal' per se? Not in Illinois.