This monthly dividend stock is an ideal source of retirement income. Many retirees face a shortfall between their Social Security benefits, savings, and actual income needs. One study found this gap to be as high as 33% for the average U.S. household. As a result, current and future retirees must find additional income sources to live comfortably. Realty Income (O -1.00%) is an excellent choice for those seeking additional income. The real estate investment trust (REIT) owns a reliable and high-quality real ...