Legal Question in Landlord & Tenant Law in Illinois

Mold is everywhere - whether it's harmful or not is a different issue - and without an air quality test you're only guessing. But if it is damaging your property, do you want to stay or move? If you want to stay you may have the right to fix the problem yourself and deduct the cost from rent over time, but that's a particular procedure. You can also contact the local building department - if this is a building code violation you may have a defense to an eviction. You may NOT be able to withhold 100% of the rent, however, and that's where you may have gone wrong. If this is going to wind up costing you anything significant, you should get an attorney involved asap.