The most important source of information about the rights and responsibilities of residential landlords and tenants is the written lease agreement. Some landlords prefer oral agreements, but it is more common for them to require the tenant's signature on a written lease—and a written lease protects the tenant more than an oral agreement. Be sure to read the lease carefully before you sign it.

If a tenant wants to change part of the lease, the tenant should discuss it with the landlord. If the landlord agrees, the landlord and tenant should decide how they want to word the change and then write it into the agreement. Both the tenant and the landlord should then initial the change. For example, many standard leases prohibit pets, but the landlord may be willing to accept a pet if the tenant puts down extra money as security (a pet deposit) to protect against any damage the pet might do.

A state’s landlord-tenant laws may provide additional rights and responsibilities and further define the rights and responsibilities identified in the lease agreement. These laws vary from state to state and are usually located in a state’s statutes.

In Illinois, the lease agreement is indeed a crucial document for both residential landlords and tenants as it outlines their rights and responsibilities. While oral agreements are legally binding in Illinois, a written lease provides clearer protection and is strongly recommended. Tenants should thoroughly review and understand the lease before signing. Any modifications to the lease should be mutually agreed upon by the tenant and landlord, documented in writing, and initialed by both parties to ensure the changes are legally enforceable. Illinois has specific landlord-tenant laws that supplement the lease agreement, such as the Illinois Residential Landlord and Tenant Act, which applies to many residential rental properties in Chicago and other locations. These laws provide additional protections and obligations that may not be fully detailed in the lease itself. It's important for both landlords and tenants to be aware of these statutory provisions as they can override or elaborate on the terms of the lease agreement.