Mr. Birnbaum began his commercial real estate career in 1972 mentoring at the side of the legendary Edward S. Gordon developing and implementing strategies for leasing vacant office towers. He brokered lease transactions for tenants, created and maintained the market research department and was responsible for hiring and training brokerage personnel. Area of expertise includes tenant representation; advising and negotiating on behalf of corporations, institutions, professional organizations and not-for profits in the acquisition and disposition of leased and owned property.

Mr. Birnbaum founded American Realty Advisors, Inc. in 1981 to provide brokerage and consulting services in the office leasing field. In 1987 he sold the firm to the successor to Merrill Lynch Commercial Services of New York, Inc. and was appointed SVP and Manager of the New York office of this publicly owned international developer (L J Hooker) and served as liason for the firm's 22 offices across America.

In 1990 he rejoined Edward S. Gordon Company, Inc which had evolved into Insignia ESG (today CBRE). Next served as Managing Director at Colliers ABR, Inc.

Over the span of his career, Mr. Birnbaum represented such notable clients as Arent Fox, Broadcort Capital, Carret & Company, LLC.,  500 Park Avenue Associates, Fuji Bank, Ltd., Kidder Peabody, Frank Russell Trust Company, KLM Royal Dutch Airlines, Paul Hastings Janofsky & Walker, Reebok International, Ltd., St. David’s School, Solow Development Corporation, Sony Corporation of America and Venable LLP.

Mr. Birnbaum has bought, sold, financed, leased and managed a variety of small properties for his own account.