In any two or more adjoining townships in the same county, otherwise entitled to come within the provisions of this act, the township trustee, clerk and treasurer of such adjoining townships are authorized to submit to a vote of the electors of such townships the question of the erection of a joint township hall for the joint benefit and use of said two or more adjoining townships: Provided, That in no event shall the total cost of said joint building and lands exceed $30,000.