After school, he worked for a time at the law firm, Shoctor, Mousseau and Starkman, and then started his own practice focusing on corporate and franchise law. In 1991, in a partnership with his Father, Katz paid $300,000 for the Canadian rights to the U.S.-based Medicine Shoppe drugstore franchise which had over 1,000 stores in the USA. In 1992, they opened the first Medicine Shoppe store and Katz founded the Katz Group of Companies which was to become the holding company for the group. In 1996, Katz purchased the storied but fading Rexall drugstore chain in Canada which at the time, only consisted of several dozen stores. The Business grew and by 1998, the Katz Group consisted of 80 Rexall stores, 30 Medicine Shoppe outlets, and a few smaller independent Retailers. In 1997, he purchased the Ontario-based, 143-store Pharma Plus drug store chain from the supermarket operator Oshawa Group for $100 million.