Section 4. Initiative. (1) The people may enact laws by initiative on all matters except appropriations of money and local or special laws.
     (2) Initiative petitions must contain the full text of the proposed measure, shall be signed by at least five percent of the qualified electors in each of at least one-third of the legislative representative districts and the total number of signers must be at least five percent of the total qualified electors of the state. Petitions shall be filed with the secretary of state at least three months prior to the election at which the measure will be voted upon.
     (3) The sufficiency of the initiative petition shall not be questioned after the election is held.