It's pretty brutal in the winter. To take advantage of business traveler's business, you have to offer a really business centric offering like being close to a place where they host a lot of conferences and have many biz amenities. Your average apartment or private room is rarely going to be attractive to biz travelers.
Seasonality in Chicago is harsh - there's much available data on its dynamics. For non business centric listings, you can basically expect anywhere from 25%-75% dropoff from your peak earnings depending on where you are located and what your winter strategy is.
There are differing winter strategies based on your market positioning that can soften the dropoff from peak earnings, do some research and position yourself well and you should get through with some profit over the winter.