By travelling in this way, Greenfield also hoped to prove that life needn't revolve around money and "keeping up with the Joneses".
It's certainly not a cocktails-and-beaches way to see the world but for those wanting to give it a shot, Greenfield shares his tips for travelling without dollars.
Pick your destination carefully
"[South America] is one of those places that's manageable but still really difficult," Greenfield says. "To try and do this across the Middle East right now, I don't know if that's even possible. South America is possible but really hard at the same time, so I felt like it's a challenge that could be met."
Don't bite off more than you can chew
He did two smaller trips with empty pockets before embarking on this cross-continent adventure.
"Those other trips made this one possible because, to be honest, they were the building blocks that allowed me to embark on this adventure," he says. "My first trip I flew down to Cabo, in Mexico, which was only 2000km from home and just one international border, and it's the United States so of course they would let me back in.
"The reason I was able to do this South American trip was definitely because I had practised it and had built that confidence from having done it prior."
Throw the guidebook away
"When I see a list of 'Top 10 Things to do in Chile' I try to hopefully never see any of that and really just go inside the houses of people who live there and see what's in their refrigerator, or what the bathroom's like, or what are the supermarkets like, what foods are there. I just want to see the everyday life and see the real aspects of the places that I visit."
But be prepared to miss out on some major attractions
"Going through Iguazu Falls, it's one of the great wonders of the world and I've seen it on programmes on Discovery Channel in the past. It's one of these incredible places that I really wanted to see and we went right through that town but because we didn't have $25 we couldn't go there. And of course if we really had the desire we could have figured out a way to work ourselves in there but also we were trying to cover so much ground in such a short time. We were hungry, we just had to figure out a way to eat."
Look for opportunities online
Greenfield recommends looking at websites like Couchsurfing.com and World Wide Opportunities on Organic Farms. "That way you can set up a place to stay for free in another country where you're working in exchange for food and lodging for the night. And also by reading the profile you know who they are and that they've been vetted, so you don't have to worry about your safety as much."
Be open-minded
"One of the biggest things I think is to get rid of your expectations," Greenfield says. "If everywhere you go and everything you're doing has expectations going into it, you're bound to set yourself up for being disappointed but if you go into it without expectations and you're taking every moment as it is, it's going to be a lot easier. If you are highly strung it's definitely going to be more challenging. You've basically got to have an adventurous personality to want to try to do something crazy like this."
Look for food in unique places
"One tip that I can really give no matter what country you're in, is go up to the markets as they're closing and ask them for whatever fruits and vegetables they have that they were going to throw away. You can just go there and fill up your bags full of fresh fruits and vegetables.
"You can basically travel across the country eating for free all foods that would have been wasted that are so good but not the most beautiful for selling on the market."
Shake off social norms
"Everyone watching this show will see me eating out of the garbage can, eating out of dumpsters and three years ago I never would have been caught dead doing that," he says. "It was only because I cared what people thought of me and just worried whether people would think negative things about me.
"Amazingly enough just by dropping that and being truly who I am and doing things for a purpose greater than myself, it's turned out that people really like me and really want to be involved in what I'm doing. It worked out so well since I dropped social norms and just really followed a passion and a purpose."
Travel with a purpose greater than yourself
"When you put yourself out there and you're helping other people and you are in service to humanity or the Earth, people are often going to want to help you more. People are attracted to people who are doing something good and who are trying to do something to make the Earth a better place. The beautiful thing is that when you're travelling with a purpose like that, people get excited and they want to get involved."
Free Ride, Saturdays from September 17, 6.30pm on Discovery Channel.
