625 ILCS 5/1-128: House trailer.

(a) A trailer or semitrailer equipped and used for living quarters or for human habitation (temporarily or permanently) rather than for the transportation of freight, goods, wares and merchandise; or

(b) A house trailer or a semitrailer which is used commercially (temporarily or permanently), that is, for the advertising, sales, display or promotion of merchandise or services, or for any other commercial purpose except the transportation of property for hire or the transportation of property for distribution by a private carrier.