I agree I would talk with people who already have listings for cleaning services. They should have a numerous amount of options for you to choose from. If you didn't want to go that route, you could also call around to family and friends. They should be able to give you suggestions and help you with everything you need! http://www.camposcleaningchicago.com
Why just foreclosures? I would target all Realtors in the area(s) were you work.
I would contact the offices in those areas. Most will allow you to leave business cards and fliers for posting in the offices.