735 ILCS 5/15-1219
"Residential real estate" means any real estate, except a single tract of agricultural real estate consisting of more than 40 acres, which is improved with a single family residence or residential condominium units or a multiple dwelling structure containing single family dwelling units for six or fewer families living independently of each other, which residence, or at least one of which condominium or dwelling units, is occupied as a principal residence either (i) if a mortgagor is an individual, by that mortgagor, that mortgagor's spouse or that mortgagor's descendants, or (ii) if a mortgagor is a trustee of a trust or an executor or administrator of an estate, by a beneficiary of that trust or estate or by such beneficiary's spouse or descendants or (iii) if a mortgagor is a corporation, by persons owning collectively at least 50 percent of the shares of voting stock of such corporation or by a spouse or descendants of such persons. The use of a portion of residential real estate for non-residential purposes shall not affect the characterization of such real estate as residential real estate. For purposes of the definition of the term "abandoned residential property" in Section 15-1200.5 of this Article, "abandoned residential property" shall not include the requirement that the real estate be occupied, or if zoned for residential development, improved with a dwelling structure.
735 ILCS 5/15-1219