The Coyle Law Office | T. Andrew Coyle
You will want the landlord to either (1) start a new lease with you as the tenant or (2) change the existing lease to include you. Either way, you will want copies of these in writing. Without those, the landlord may begin eviction proceedings at any time (of course, if you're paying rent, I would imagine he would not want to do that).
Answer Applies to: Illinois