Legal Question in Landlord & Tenant Law in Illinois

You provided both insufficient information and irrelevant information. Apparently you had some kind of purchase rights, which you did not exercise, so your narrative about it appears irrelevant unless monies you paid were somehow added to your security deposit, which is not normally the case. If anything, at the time of closing of a sale on a rent-to-own, the security deposit is a credit against the purchase price unless there was something the landlord was supposed to repair, but that is all contractually based. So it appears the general lease provisions apply. As to the security deposit, it will depend on two critical factors: (a) was it Chicago or another community where there are specific ordinances regarding security deposits that may supersede Illinois law, and (b) even in a community with no such ordinances, the return of security is dependent on the number of units in the building. Since you say it is a "duplex" it would appear there are only two units in the "building" (although if this building and others are under common management and the total units are more than 5, you may have some rights under the Illinois statutes. If none of the above apply, your lease controls, and if there are no time parameters for return of your security, the time period must be 'reasonable'. In Illinois as its basic statutes provide for a return process of 45 days that includes notification of any monies that may be withheld, a 50 day period is beginning to become unreasonable if you had no such notice, but now it may be up to you to file suit for any refund. Time to have an attorney review the facts and your lease completely to be certain of your rights.