Loans made by credit unions may be payable to the members in a lump sum or in installments, of the following types:
a. Loans to be repaid in a lump sum by the member;
b. Loans to be repaid in two or more installments, which installments are approximately equal in amount;
c. A line of credit to be made available to the member by the credit union, whereby funds may be advanced to the member pursuant to the member's written authorization and repaid upon terms as established by the board.