There shall be an initial trust corpus of not less than $3,000,000 which corpus shall be a trust fund to secure enforcement of the interindemnity arrangement. The average initial contribution to such corpus shall be not less than $20,000 per member participating in the interindemnity arrangement. No such interindemnity arrangement shall become operative until the requisite minimum reserve trust fund has been established by such participating members. The commissioner shall have the power to investigate and verify the amounts specified by law.