Except as hereinafter provided, the corporate purpose of a corporation shall be to render service to its members only. Any person may become and remain a member if such person shall use energy supplied by such corporation and shall comply with the terms and conditions in respect to membership contained in the bylaws of such corporation, which terms and conditions shall be nondiscriminatory. Any person who shall agree to use energy supplied by the corporation from an existing line or from a line the construction of which has been authorized or commenced by the corporation may be admitted to membership in the corporation prior to such use upon complying with the other terms and conditions with respect to membership contained in the certificate of incorporation or in the bylaws. The membership fee of the corporation shall be fixed by the board of directors. Should the corporation acquire any electric facilities already dedicated or devoted to the public use it may, for the purpose of continuing existing service and avoiding hardship, continue to serve the persons served directly from such facilities at the times of such acquisition without requiring that such persons become members. In no event shall the number of such nonmembers served exceed forty-nine percent (49%) of the total number of persons served by the corporation. Such nonmember customers shall have the right to become members upon nondiscriminatory terms.