It used to be 1st months rent + deposit but many landlords are going away from this and asking for 1 months rent + an upfront fee (not a deposit) in case of any damages. Kind of like a non refundable move in fee.
Either a security deposit or now a "move in fee" are being charged in Chicago. This is to protect the property and make sure you take care of it. If you move out and the place is a mess the landlord will charge you for cleaning and repairing. The charges are taken out of your security deposit.
Yup, rent and security deposit are normally due at the same time.
That said, depending when you contract you may be able to give the security deposit then the 1st months rent on the 1st, or day before, really depends on the landlords flexibility and your qualifications.
Usually to finalize the unit, after the application is finalized, the security deposit AND the first month's rent are due to get the landlord to sign off on the lease. There are always exceptions. The landlord may only require one or the other to sign the lease. Some buildings will have very small deposit requirements. If you are renting a condos, expect to pay 1 month rent and 1 month security deposit.