CHICAGO — Essex Realty Group Inc. has brokered the sale of a condominium building in Oak Park, a suburb of Chicago, for $2 million. The property, located at 922-924 Ontario St., features 13 one-bedroom units. Ontario Association purchased all of the units in what is known as a condo deconversion. Under the Condominium Property Act in Illinois, unit owners can elect to sell a condo property if 75 percent or more are in agreement. Owners then have the option to either move out or to leaseback from the new owner. Jim Darrow and Jordan Gottlieb of Essex arranged the sale on behalf of the buyer.