This story is part of CNBC Make It's Millennial Money series, which details how people around the world earn, spend and save their money.

In 2011, like many 18-year-olds, Darren Thedieck wasn't sure what he wanted. He thought briefly about studying to become a dentist, "but I was nowhere close to that," he says. Plus, he was worried about the prospect of racking up student debt.

Knowing he wanted to travel the world and seeking financial stability, he enlisted in the U.S. Air Force, hoping to maybe get into the medical field that way.

Instead, he was encouraged to work in IT — a potentially lucrative field in the private sector — at an E-1 Basic Airman's base pay of about $1,400 a month.

Thedieck, now 31, is still in the military, and has gotten an awful lot of what he's wanted ever since.

Travel the world? Check. After basic training and a stint in Las Vegas, Thedieck took assignments in England, South Korea, Germany and his current posting in Aviano, Italy — about an hour's drive from Venice.

He's gotten financial stability too. Thedieck has steadily risen in rank and pay over his 12-plus years in the military while dutifully stashing away cash in a variety of investment accounts. Between his base pay and allowances, he pulled in $9,134 in March, which works out to an annual income of about $110,000.

He's been slowly but surely working toward a degree in finance using military tuition assistance, and in 2017 began teaching free personal finance classes for fellow servicemembers online and in person.  

Another person he helped with money management: his wife Naudia, who he met in Germany in 2021. At the time, she had about $25,000 in student, credit card and automotive debt.

"Me being a finance guy, I kind of got that conversation going early on in our relationship. We got together and made a plan to cut unnecessary expenses," Thedieck says. "And although we didn't completely join our finances together at that point, we started working on a monthly budget for her in order to enable her to aggressively pay down her debt."

By the time the couple got married last April — a destination wedding in Denmark — they were debt free.

The couple welcomed their first child in February, and Thedieck already has bright plans for the future. His investments currently total more than $500,000 — a figure he hopes to push to $1 million in the next five years.

A few years after that, he'll be eligible for retirement from the military with a pension worth half his base pay. Early retirement at age 38 will just be the start of his second act.

Saving on a military salary

Thedieck was interested in saving and investing long before he joined the Air Force.

"Our family didn't have a whole lot of money coming up," he says. "I had to see my mom struggle at times financially. Part of that inspired me to do better for myself financially."

By 16, he was working at grocery stores and reading about how he could get the money he saved to grow. "Some of my early influences were through books — Warren Buffett, Benjamin Graham, figures of that nature," he says.

Though he admits he didn't necessarily start with the titans of the investing world. "I went to the bookstore and picked up, plain and simple, 'Stock Investing for Dummies.'"

At 18, he opened a Roth individual retirement account, and soon began maximizing his contributions. He also began contributing to his Thrift Savings Plan — the government's version of a 401(k).

Thedieck credits the prodigious amount he's invested in part to the way that he's compensated. "The pay structure in the military allows me to aggressively save because a lot of the income that I get in the form of allowances aren't taxed," he says. "It's very tax-advantageous to serve in the military."

In March, Thiedeck's base pay was about $4,650. From there, he sees deductions for federal taxes, Medicare, Social Security and group life insurance. He also receives three more sources of income in the form of entitlements: about $460 for food, $3,294 for housing, utilities and home maintenance and a $729 cost-of-living allowance.

When you live abroad, those allowances can go an awfully long way, Thedieck says.

"Cost of living in Italy is actually pretty affordable in comparison to most parts of the United States," he says. "In rent alone, we're in a pretty nice house — a four-bed, two-bath — and we pay roughly €1,650 which translates to about $1,800 [per month]."

How he spends his money

The low cost of living has helped Darren and Naudia keep their budget under control, but it's taken planning as well.

Naudia left her job at Service Credit Union when the couple moved to Italy in 2023, both to prepare for the arrival of their child and to avoid working visa red tape in a new country. Moving to one salary has made things a little trickier, but still manageable, Thedieck says.

"That's forced us to be even more intentional with our finances and how we spend and save," he says. "Now that we're down to one income, we actually conduct monthly financial meetings as a family."

Here's where their money went in March 2024.

• Housing and utilities: $2,279 for rent, Wi-Fi, electricity and home fuel
• Savings and investments: $2,230 deposited into his TSP and taxable brokerage account
• Groceries: $737
• Discretionary: $683 on household items, wellness treatments, entertainment and travel
• Dining: $543 on meals, coffee and drinks
• Car repair: $350
• Gas: $255
• Insurance: $145 on health, dental, auto and life policies
• Subscriptions: $50 for Apple, Disney, Netflix and Spotify
• Phones: $24

At a glance, a few expenses on that list feel low while others seem to be downright missing.

No debt paydown? Thedieck and his wife own their vehicles outright. Naudia is debt-free after aggressively paying down her loans, and Thedieck never had any debt in the first place. He also pays off his credit card balance multiple times per month.

He's been working toward his bachelor's degree using $4,500 a year worth of tuition assistance rather than paying out of pocket or using his GI Bill. As a result, he may be able to transfer his benefit to his child, who could attend college on the military's dime.

The cost of raising a child is partially reflected in the couple's household and grocery bills, but other baby expenses have been very low thanks to the generosity of the community on base. They still haven't gone through all the diapers Naudia received at her baby shower.

"We have spent roughly $500 of our own money on our baby, from a 3-in-1 combo stroller to various smaller items," Thedieck says. "Everything else has been received through our registry and friends' donations." 

Of course, the couple is willing to spend on things that matter to them. Throughout his career in the military, Thedieck has been willing to spend on travel, and says the budget gets a little looser when he and Naudia are on the road together.

"We want to make the most of those moments and not think so much about how much it costs to do things, but put more value on the experiences," Thedieck says. The same goes for spending on health and wellness.

They're even willing to extend the food budget if it means indulging in a few more macchiatos or savoring the local cuisine. For Thedieck, it's all about finding a balance between spending and saving.

"I understood from an early age that I wanted to prepare a secure future for myself, especially in anticipation of a family," he says. "But I also realize the importance of living in the now and making the most of that. So I tried to travel as much as I could, while also setting myself up for the future."

Future plans and FIRE

For many savers, "the future" is code for retirement, and for Thedieck it is, too. He's just planning for it to arrive sooner than most.

Thedieck is aiming for FIRE, short for financial independence retire early.

Adherents to the FIRE movement aim to stash a large portion of their income into investment accounts. The goal is to reach their so-called FIRE number — the amount in your portfolio from which you can safely withdraw a certain percentage, often 4%, in perpetuity each year to totally cover your living expenses.

As a member of the military, Thedieck's road looks a little different since he'll have an extra source of income in the form of a half-base-pay pension.

If he wanted, Thedieck could supplement that income with withdrawals from his investing accounts. He currently invests $1,300 a month into a taxable brokerage account and another $930 into his TSP. All told, his mix of investments is currently worth more than $500,000.

Right now, though, the plan is for that money to provide a financial "cushion" for the family, Thedieck says. Instead of full retirement after military life, both he and Naudia plan to take off in a new direction.

Naudia plans to go back to work. Thedieck, meanwhile, hopes to launch his financial classes as a small business while also taking on a new rank: stay-at-home dad.

"I'm going to run my online finance business for a little bit. That'll allow me that benefit to stay at home, run that, but also just kind of hang out and relax and enjoy my life a little bit more, just by taking care of our children as well as the household," Thedieck says.

Until then, Thedieck and his family will go wherever the Air Force stations him. Once he retires, though, the plan is to move back to Europe, where cost of living is low and opportunities to travel are abundant.

While Portugal holds appeal as a home base, "we had the idea to move every six months to a year to new locations in Europe," Thedieck says. "We've talked about living in London for a year, living in Dublin, Ireland, for a year, places like that, so that we can kind of get a feel for what the life is like."

The experience, the couple hopes, will be enriching not only for them, but for their child, along with any more they might have on the way.

"While it might be a little bit more frequent moving for them, it'll really offer them so many diverse opportunities that American children just don't get by being home."

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