Such corporations must not contract any debts or liabilities in excess of the amount of money in the treasury at the time of contract except for the purchase of real property, for which they may create a debt not exceeding Three Thousand Dollars ($3,000.00), secured by mortgage on the property of the corporation. The directors who vote therefor shall be personally liable for any debt contracted or incurred in violation of this section.

R.L. 1910, § 23.