Justin McCurry, a father of three based in Raleigh, North Carolina, quit his engineering job in 2013 and retired at age 33. His wife, Kaisorn, joined him in early retirement in 2016 at age 38.
"Neither of us ever reached a six-figure salary, with my salary topping out at $69,000 and [Kaisorn's] at $74,000," Justin writes on his blog, Root of Good, which explains how they built a seven-figure portfolio in 10 years to retire early.
They aim to spend $40,000 a year, or $3,333 per month, but, since their portfolio has gone up quite a bit in the past couple of years, they're going to start "giving ourselves permission to spend $5,000, $10,000 or $20,000 more than that if we find something worthwhile to spend it on," Justin tells CNBC Make It.
The McCurrys have spent $22,335 over the first 10 months of 2018. Their most expensive month has been June, when they spent $3,554, slightly above their target. That month, they prepaid $1,136 on their water and electricity bills and spent $858 on home insurance for the year and car insurance for six months.
Some months, they'll spend significantly less, like September 2018, when they spent just $1,342. Their biggest two categories of spending that month were food — they spent $596 on groceries — and travel, which set them back $494.
Ultimately, flexibility is key in early retirement: "You may have to spend less if the markets go down. Or, you may be able to spend more than what you originally budgeted for," says Justin. "As long as you're OK cutting back on some of the wants if your portfolio goes down, then you can still cover your needs without worrying about depleting your assets prematurely."
They worked strategically for years in order to get to a comfortable financial place. By tracking their expenses and living frugally in Raleigh, "every year we saved more than half of our income," Justin says. At their peak, earnings-wise, they made a combined $138,000 and saved up to 70 percent of it.
They didn't just save, either: They put their money to work. "We consistently pumped our savings into 401(k)'s, IRA's, HSA's, 529's, and regular brokerage accounts," Justin writes. "These investments grew enormously over roughly 10 years and made us financially independent today."
You can see a detailed breakdown of how their money grew from $64,000 in 2004 to $1.3 million in 2014 on their blog.