After school, he worked as a commercial leasing broker with fellow graduate Arthur Rubloff. In 1929, he partnered with grain trader and real estate investor, James E. Norris, who was impressed with how Wirtz handled one of his real estate transactions. During the Great Depression, the Wirtz-Norris partnership began to purchase arenas at much reduced prices. In 1933, they purchased the Olympia Stadium in Detroit, Michigan and its hockey franchise, the Detroit Falcons, which they renamed the Detroit Red Wings for $100,000. In 1935, they purchased the Chicago Stadium. Wirtz was able fill his stadiums after securing and booking the Hollywood Ice Revue produced by and starring Olympic ice skating champion Sonja Henie. He used the proceeds to pay off the mortgage on the Chicago Stadium and also purchase Madison Square Garden in New York City and the St. Louis Arena. In 1946, he and James D. Norris helped Bill Tobin purchase the nearly bankrupt Chicago Blackhawks.