bike storage in Chicago?

My wife and I are going to be out of the country for a year, and we're looking for someplace inexpensive to store our bikes. Our friends can't offer us space at the moment, unfortunately. We're going to be putting some other stuff in storage, but the bikes (2 of them) take up enough space that we'd have to get a bigger storage unit.

Does anybody in the city offer anything like this? Milwaukee might also work. I've called a couple shops but haven't found anything yet.