Günter Koller began working as an attorney at the commercial law firm BEITEN BURKHARDT MITTEL & Wegner in 1994, where he specialised in real estate and banking law. In 1997, he joined with several colleagues to found GSK, a law firm specialising in real estate, banking and finance law. He left the firm in mid-2001 and became Managing Director of Wilhelm von Finck Hauptverwaltung GmbH, Munich. The family office supports Wilhelm von Finck and two other wealthy clients with regard to all asset management matters except for financial services. Günter Koller is the Deputy Chairman of the Supervisory Board of Quantum Immobilien AG, Hamburg and Isarklinik AG, Munich, and he is a Member of the Supervisory Boards of Accumulata AG, GIEAG, Hammer AG, all in Munich, and 6B47 Real Estate Investors AG in Vienna. He is also a Member of the Advisory Board of Paramount REIT PGRE, New York.