As long as the title is legal and the name on the title is the person that signs it as the seller ( with date and mileage) -and- the buyer section is blank and ready for your own name and signature, there is no problem. IL just wants $25 for a private party vehicle use tax transaction, $95 fee for the title filing and $39 for plates ( you will have to fill out the tax form, title app and sign of course)
I have brought in titles for bikes that had not been current on registration for decades.
The only things I would stay away from are titles that do not have a blank transfer section for the buyer's name and certainly never, ever buy a bike without a title and expect to get one in IL by filling out some "magic paperwork". It takes a court bond to initiate the filing for vin check, about a year of waiting and about $300 just to get a salvage title from them