An association may invest in land on which to erect an office building, an office building or buildings and appurtenances, for the transaction of such association’s business, or for the transaction of such business and for rental, but no such investment may be made if the total amount of all investments of the association in such building or buildings exceeds the aggregate amount of the association’s outstanding shares of guaranty capital, reserves available for losses and surplus, unless the deputy director, on a proper showing, shall approve a larger amount consistent with the needs of the association’s business and its immediate expansion. An association shall not purchase an office building, or any part of an office building, or land on which to erect an office building, from an affiliated institution, from an officer, director or employee of such association, or from a corporation or association in which any officer, director or employee is a stockholder or is an officer, director or employee, or from a partnership in which any officer, director or employee is a partner, without the prior written approval of the deputy director.