Brandon, who asked to withhold his last name to maintain his privacy, has been living out of a 128-square-foot truck for over a year to save on rent.

His advice for making early retirement a reality.

1. Make a plan
"Get a plan together as soon as you can," he tells CNBC. "The sooner you have a plan, the sooner you'll see your contributions compounding into something meaningful and substantial."

2. Maximize tax-advantaged accounts
Figure out which tax-advantaged accounts you have available to you and how much you can contribute to them.

3. Streamline
Finally, "evaluate your priorities and cut out the cruft from your life," says Brandon. (Cruft is a coding-derived word for redundant and unnecessary clutter.)

Overall, Brandon says, "decreasing your spending is usually a lot easier and more effective than increasing your income." Plus, reining in your spending is something you can start doing right away. It's within your control.

And, while the ideal time to establish a plan for financial independence is when you first enter the workforce, he says, "the second best time is now."

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