All loans are a shared transaction between the lenders willing to lend (or originate) funds and the borrowers willing to accept the money at the agreed upon fees/rates.
I'm not sure what your real question is. "The" indicates a singular source and there is no "single" source for sub-prime loans. "Is" is a present tense verb meaning "now doing" But I'm not sure because of a disconnect in your vernacular if you are trying to find a lender that currently services sub-prime borrowers for properties in the Chicago area ? Or are you trying to determine which lenders might have been previously responsible for making loans to sub-prime borrowers?
Please give us more if so we can help you.