Dustin Johnson, the world's top ranked golfer, won last year's U.S. Open and its $1.8 million paycheck. He made $9.3 million during the 2016 season and has raked in more than $3.6 million already this year to push his career earnings over $42 million. And that's not counting endorsement deals. He also is engaged to the daughter of hockey legend Wayne Gretzky.

Life in golf is great, right? It certainly can be at the top. But to understand the financial burdens many lower-level pros face, you should know about one of Johnson's college teammates, Zack Byrd.

After golfing together three years at Coastal Carolina University, where Byrd still holds the school record for lowest score, the two each played the 2011 U.S. Open. Johnson made $76,455 for finishing 23rd. Byrd missed the cut and received $2,000, which didn't cover his expenses for the week.

Their career earnings gap is even wider. While Johnson has made a fortune, Byrd estimates his seven-year pro earnings at probably under $250,000, possibly less than his expenses have been.

Zack Byrd played in the 2011 U.S. Open, two years after he turned pro, but that's the only time he has competed in a PGA Tour event. Rafael Suanes/USA TODAY Sports

In order to help make ends meet after his wife, Alison, had their first child last winter, Byrd started his own travel agency. Having competed on three continents (and adding a fourth in 2017), Byrd knows travel well, especially the costs. He once spent $5,000 to fly from Myrtle Beach, South Carolina, to Santiago, Chile, for an event on the Web.com Tour, the PGA Tour's developmental circuit.

"It was early in the year, and it was a start I wasn't expecting to get," said Byrd, who recently turned 31. "I found out Sunday, and I had to leave Monday. ... If I had made that cut I probably would have played the rest of the season. It was that close. It was five years ago, and that one cut could have jump-started my career."

Byrd did not make the cut. It was $5,000 down the drain.

"Everybody asks me what it's like, and I'm like, 'Just imagine gambling every day of your life,'" Byrd said. "It's a gamble. You gamble on yourself, and you hope to win."

Yes, he plays golf professionally, but Byrd and his family live paycheck to paycheck.

"It's stressful; it's hard," he said. "I can't tell you the last time I woke up and wasn't stressed out. It's constant stress."

PAUL APYAN, WHO CHRONICLES his playing experiences using the Twitter handle @LifeonMiniTours, compares the lower tours to baseball's minor leagues.

"It's Single-A to Double-A depending on the level of the event," Apyan, 30, said. "I guess high Single-A is the best way to put it."

Unlike low-level golfers, however, minor league baseball players don't have to worry about travel, lodging and other incidental expenses.

Australian native Bryden MacPherson, who competed primarily on the Web.com Tour in 2016, figured his expenses were around $10,000 more than his winnings for the year.

"How much money you spend is a really common thing that astounds a lot of people," MacPherson, 26, said. "They don't understand you have to spend $3,000, maybe $3,500, in a week just coming out of your pocket before you even tee it up. Then you have to play with that hanging over you."

Bryden MacPherson of Australia, shown lining up a putt during a 2015 tournament in Colombia, earned around $10,000 less than he spent on his golf career in 2016. Matthew Stockman/Getty Images

Byrd estimates annual expenses typically average around $50,000, though he can scrape by on $30,000 or less. "I have mastered the art of stretching a penny, and I am probably one of the cheapest guys in the world," he said.

Expenses aren't much different for the women on the Symetra Tour, the LPGA Tour's counterpart to the Web.com Tour, but there's even less prize money available. "There are a lot of expenses that go into it that people don't realize," said Ericka Schneider, 25, who made 16 starts on the Symetra Tour in 2016. "A lot of us have trainers, a lot of us have swing coaches. Some people have putting coaches, sports psychologists. Caddies are an expense."

Sweden's Madalene Sagstrom (a tour record $167,064) and Ally McDonald of the U.S. ($110,359) were the only Symetra Tour players to collect six figures in earnings in 2016. A third of the players in the top 100 took in under $15,000, less than someone working 40 hours a week for the U.S. minimum wage. Schneider says she totaled roughly $5,000 on the Symetra Tour and in various other events last year while spending about $20,000.

When she was in high school, Erika Schneider partnered with Jeff Sluman in a senior tour event at Pebble Beach. Now 25, Schneider has learned how hard it is to earn a living playing golf. Chris Condon/Getty Images

While still a far cry from the PGA Tour payouts, the winning prizes on the Web.com Tour usually are more than $100,000. The top 25 money winners each year earn PGA Tour cards, and last year those players earned between $150,000 and $450,000. Half of the 243 golfers on the 2016 money list, however, earned less than $30,000 on the Web.com Tour, though many had additional winnings on the other tours.

Among those are the Canada, Latinoamerica and China tours, which generally have smaller purses than Web.com. Then there are the regional mini-tours, where the payouts can be even lower.

Apyan will be playing his third season on the PGA Tour Latinoamerica this year. While the experience has been memorable -- he recalls playing in Guatemala at the base of an erupting volcano -- it also has been very expensive. He made about a dozen flights to South and Central America last year at a cost of $11,000, and his total expenses were nearly $42,000. His tournament earnings were $57,000.

He says that his wife, Leah, who works for the Bayer corporation, "keeps us above the poverty line."

While travel and lodging might be the biggest expenses, they aren't the only ones. The Symetra Tour charges $500 for a tournament entry. Mini-tours sometimes charge $1,000 or more for entry and tack on greens fees for practice rounds.

"Some weeks it's a cart fee of 40 to 50 dollars," Apyan said. "Guys will go online to GolfNow.com for a lower rate than the event was offering and book it through that to save money."

Paul Apyan hits a shot during last year's PGA Tour Latinoamerica Tour event in Nicaragua, where he tied for 47th to earn $757.75. Sean M. Haffey/Getty Images

As Australian-born veteran player Scott Gardiner said: "The golf world is upside down. When you're at the top they give you everything for free, and when you're at the bottom you pay for everything."

Worrying about expenses can have a negative effect on players' performance. Rather than concentrating on a shot, they can get distracted thinking about how high they have to finish to cover costs.

"That's the thing I had to fight with. I was thinking about things that weren't pertinent to me playing golf," said Schneider, who covers some of her touring expenses by working as a playing pro and in the pro shop at the Waterlefe Golf & River Club in Bradenton, Florida. "Being out on the golf course and focusing on whether you're going to make the cut and going to make money and going to be able to play next week is not something that's going to help you hit that good shot right now."

FORTUNATELY FOR BYRD, he now has monetary support other than from his wife. Keith Hinton, a Virginia realtor, and Nate Carl offered to cover Byrd's expenses -- though he will hand them 5 percent of his winnings and has a long-term agreement to repay them. Apyan also has backers, though they take a larger cut of his winnings in return.

"There is very little money in mini-tours, so you're really helping somebody make it on the PGA Tour and then maybe make some money there," said Hinton, a former aspiring golfer who can relate to Byrd's plight. "The important part was I had people do it for me 20 years ago. It's a way of paying back.''

With his financial stress reduced, Byrd will play on the Sunshine Tour in South Africa this spring. He says it pays a little less than Canadian tours but costs much less. Entry fees are just $8, and hotels can be had for $40 a night. He hopes to play well enough in South Africa that he can qualify for the European Tour, where the money is far superior; 59 players already have earned in excess of €100,000 this season (approximately $105,000), with runaway leader Tommy Fleetwood eclipsing €1.5 million ($1.6 million).

Byrd will spend the upcoming season in South Africa on the Sunshine Tour, where he hopes to play well enough to climb up to the European Tour. Enrique Berardi/Getty Images

"That's why I'm excited about South Africa," Byrd said. "It's a different mindset that I've never been able to have. It's a lot freer, more goal-oriented. Not worried about, 'I have to make this cut so I can put some money in the bank so I play the next week as well.' I don't have to worry about that.

"I might look at myself a year off and say that was the stupidest thing I've ever done. And I might look at myself and say, 'Wow, that was the smartest thing you could have done for your career.'"

After all he has been through, Byrd says anyone with "half sanity" probably would have quit by now. And he might have to after this year because of family responsibilities.

"I honestly think that this will be it this year if I don't get some good status for next year where I feel I can actually make some real money," he said.

Apyan says he considered calling it quits after his son, Cameron, was born, in 2015.

"Before that I had missed 12 cuts in six months, eight by one shot and two by two," he said. "I was like, 'Do I really want to keep playing? I've got a family, and I need to provide for them. And I keep doing everything I can, but I just keep coming up one shot short. Or a bad break here or bad bounce there.'

"And then I played in two events in Iowa, and I made $25,000. I won an event. If I had finished second that week, I wouldn't be playing golf. But since I won, I got to keep going."

Scott Gardiner watches his putt roll at last year's Web.com Tour Utah Championship, where he tied for 32nd place to earn $3,190. In 2013, Gardiner totaled $347,000 in winnings on the PGA Tour and Web.com Tour. Steve Dykes/Getty Images

Gardiner has earned close to $1.8 million on the PGA Tour and Web.com Tour in his career. Now 40 with carpal tunnel syndrome in his left hand and a pinched nerve in his elbow, he is mainly teaching golf in Fayetteville, Arkansas. He warns against thinking too much about the expenses.

"When you have to fight for something, you're experiences are greater. It builds character, let's say," Gardiner said. "Whether it's golf or the next stage of your life, you have to keep the right attitude. If you're thinking about that other person making $40 million and you're in the red, that's not concentrating on what's in front of you.

"I really enjoy seeing my friends succeed, but it's not a competition. It's about you being better every day and taking the opportunity that's in front of you."

And regardless of the financial bottom line, the value of getting to play the sport you love and to see the world while doing so shouldn't be underestimated.

"You could look at it and say, 'He's only made $30,000 in 4½ years,' but I look at it as I've had the most amazing experiences," MacPherson said. "You learn so much about everything by traveling the world and dealing with things that most people don't have to deal with. You learn so much about yourself and so many things you can do that you didn't think you could.

"That's priceless. I wouldn't trade it for anything."

Apyan says he spent $11,000 on airfare last year while playing on the PGA Tour Latinoamerica. Enrique Berardi/Getty Images

Sometimes, it's all about perspective.

"I watched a caddie on the Guatemala course by the volcano," Apyan recalled. "He rolled his ankle with three holes to go. When he was done the [player] said, 'I will pay you half of tomorrow if you need to get your ankle taken care of.' The caddy said, 'No, I will get a shot, I will take a pill and I will be ready so I can make that other $25."'

Apyan says he has also seen caddies drive 18 hours to make $40 U.S. and eight hours to make $45.

"They want the chance to do better," Apyan said. "They're not asking for someone to give it to them, they're asking for someone to give them an opportunity.

"Nobody wants the story about how great it is. They need to know the low point and how fortunate we are."

Maybe not as fortunate as Dustin Johnson. But as Gardiner said, "There aren't many Dustin Johnsons out there."

But some of the mini-tour warriors and relentless grinders out there are destined to claw their way into the big time. Plenty keep trying.

"The only reason I would give up is if there is absolutely no avenue with which I could keep doing it," MacPherson said. "As long as there is light at the end of the tunnel, I'm still climbing toward it."