(a) The tax required by this article to be paid on instruments securing long-term notes secured by real estate shall be exclusive of all other taxes on the notes. Such intangible property shall not be taxed in any manner other than as provided in this article by the state, any county, or any municipality, nor shall the owner or holder of the property be required to pay any other tax on the property.

(b) Nothing contained in this Code section shall be construed to exempt any owner or holder of property taxed pursuant to this article from the payment of income taxes otherwise due on account of income derived from the property.