Section 16. With the approval of the commissioner of insurance, a corporation subject to this chapter, alone or with one or more nonprofit corporations, the real estate of which is exempt from taxation, may acquire real estate it reasonably expects to use in whole or in part for conducting the business of such corporation or corporations. Real estate so acquired may be leased to other occupants, and when so leased, the exemption from taxes on real estate granted by this chapter or granted by any provision of the general laws to a co-owner shall not apply to that portion of the real estate which is so leased unless such other occupant occupies the leased premises for its purposes and is (a) a charitable organization, as defined in section five of chapter fifty-nine, or (b) a nonprofit corporation organized under the laws of the commonwealth to provide any kind of health service, the real estate of which is exempt from taxation. Nothing in this paragraph shall limit the general investment powers set forth in this section.

No investment, sale or loan shall be made which has not first been authorized by the board of directors, or by a committee thereof charged with the duty of investing or loaning the funds of the corporation; nor shall any deposit be made in a bank or banking institution unless such bank or banking institution has first been approved as a bank of deposit by the board of directors or said committee thereof, and unless the vote authorizing such investment, sale or loan or approval of the place of deposit has been duly recorded in the books of the corporation.