For many, early retirement feels like a far-off dream.
But for others, it's a concrete reality. Just ask Scott Alan Turner, who dug himself out of $70,000 worth of debt to become a millionaire at 35 and retire in his 40s. Or Justin and Kaisorn McCurry, who saved 70 percent of their income and retired in their 30s.
What would it take for you to retire by 40?
For starters, you'd likely need to increase your savings in a big way. While saving 15 to 25 percent per paycheck is recommended to be able to retire at 67, you'll need to increase that to around 50 percent to retire by 40, Kimmie Greene, money expert at Intuit and spokeswoman for Mint.com, tells CNBC Make It.
However, even if putting half of your paycheck in the bank each month is feasible, it's not the enough to guarantee a successful early retirement plan.