Legal Question in Real Estate Law in Illinois

http://www.cookcountytreasurer.com/taxdates.aspx?ntopicid=81

The above link will give basic information on tax sales. You will want to review whether taxes were already sold. If you want to participate in the next tax sale, you will need to follow procedures to register. In the long run, it will be in your interest to work with a law firm that routinely handles Cook County tax sale matters as the requirements to eventual get a tax deed are very specific.

I agree w/ Mr. Repay. In addition, there are ways of finding out who the owner is if you are serious about buying it. Talk to a real estate attorney or at a minimum contact a title insurance company. You can also register a complaint with the local building department and they will have the ability to go after the owner to clean up the situation at the very least - towns have that power and to lien properties they have to keep up for the owners, IF the town is prepared to take those steps, and if not they do have the power to issue code violation notices and take the owner to court to get things corrected, especially if the place is creating a "public nuisance" that is affecting you and other neighbors.