To the OP: s
Go on the Cook County Recorder of Deeds website. Search the property's PIN number (it's 15 digits I believe, you can get it off the MLS listing) or search the owners name if you know it, which it sounds like you do. You can see what the final sale price was, and you can even see how much of a loan the owner took out, giving you a ballpark idea of how much they have in it. The document that says Warranty Deed is usually the closing price. Sometimes all the info is on there, sometimes not, but its easy and free so search. Good luck.
Baird and Warner
I would consult with your Realtor and they can pull up this information. They can also pull up information regarding the sales of similar units in the building. I would be happy to help if you are not currently working with someone.
Americorp Real Estate
Brokers Associate, e-PRO