“Income is the No. 1 key as you get older,” says Dwain Phelps, founder and CEO of Phelps Financial Group in Kennesaw, Georgia. Phelps says dividend income is something investors should be planning for starting in their 40s. “Dividend income can be an excellent source of income, but it’s important that investors understand the differences between interest income and dividend income,” says Andrew Crowell, vice chairman of wealth management at D.A. Davidson & Co. in Los Angeles.