(1) Every association may issue and sell an unlimited number of shares of the following types, as described in this section:
(a) "Investment shares" are shares on which the full payment has been made and on which dividends shall be paid in cash.
(b) "Savings shares" are shares on which an initial payment has been made, and upon which further payments are to be made at such times and in such amounts as are optional with the member, and on which dividends shall be credited unless otherwise agreed that all or part shall be paid in cash.
(c) "Short-term savings shares" are shares which are to be withdrawn in less than twenty-four months from the date on which such share account is opened, or a share account established for the purpose of accumulating funds to pay taxes or insurance premiums, or both, in connection with a loan on the security of a lien on real estate. No association shall be required to distribute earnings on short-term savings shares.