Legal Question in Real Estate Law in Illinois

A lease is a contract for the use of property for a given time. It is between a landlord and a tenant. It depends who the 'provider' signed the contract with. If with the landlord, then it could be. Without seeing it I can't say. Is the landlord promising to pay part of the rent? Section 8? Sublet?

To be enforceable, an agreement must be between two parties. If someone just signs a paper stating that they will pay, that is not very enforceable. I think that you need to go to one of the not-for-profit legal aid societies and have them look at it. John Marshall Law School has one that specializes in Real Estate, maybe they can help.

Could you be more specific about what you mean by the "provider"? If you mean the landlord will actually provide the housing and subsidize the rent in any way, the separate agreement to subsidize is not the lease itself. But that separate may be what is called "collateral" to the lease, and without the lease the subsidy payment itself may be of no value to prove you are entitled to occupy the rental unit itself. A lease for a year or less in Illinois can be oral (not in writing) but with this kind of separate agreement it would make most sense if both were in writing.