When 37-year-old Leonardo Leo Grand lost his job at an insurance company two years ago, he found himself out on the streets of New York.

"I couldn't afford the rent where I was staying. They built these expensive condominiums and the rent just skyrocketed, and I got evicted," he says. He lived at a drop-in center for a while, but eventually left because he didn't like it there.

But instead of giving way to despair, Grand saw his situation as an opportunity to do things he had never been able to do before. For one, he spent many of his days at a computer store to "do research on all the Macs."

He also had time to reflect on another passion of his: How to protect the environment.

"Global warming became an extremely important issue for me due to the severe drought in the mid-west and California," he explains. "There's obviously too much CO2 in the atmosphere. It's got to be modern living that's at least speeding up the process of global warming."

Chance meeting

It was plain luck that Grand met Patrick McConlogue, a 23-year-old programmer who walked past him on his way to work in Manhattan five months long. McConlogue says he noticed Grand while he was exercising with a pair of chains he had found on the streets.

"I saw him lifting these old, rusty boat chains. There was a level of intensity which said to me he didn't want to step out of the game. He's interested in doing something," McConlogue says. "So something snapped for me."

The next day, he sought out Grand and presented him with a choice: He could either take $100 in cash - or get trained in software engineering and app coding. Grand took him up on the training, but admits he initially thought the offer was too good to be true.

"But he did show up with the laptop the next day and, and history was made, so to speak," Grand says, laughing.

McConlogue gave Grand a cheap laptop and three books on computer code. Every morning before work, the programmer came and tutored Grand on a park bench for an hour. Then, McConlogue would head off to his office job while Grand continued studying on his own.

Carpooling to help save the environment

The impromptu training course went on for several months. And it paid off: Grand recently launched his own app, "Trees for Cars," which helps users find people with whom they can carpool.

"The main objective is less cars on the roads. Less cars period, via carpooling," Grand says.

With McConlogue's guidance, Grand wrote each of the 3,621 lines of code that dictate the look and functionality of "Trees for Cars."

"You can be a driver for your neighbor or neighbors, saving them gas money, saving them money and wear and tear on their vehicle and socializing with them, networking with them under the umbrella of saving the environment," Grand adds.

Within the first five days of its release, "Trees for Cars" shot to number five in the app download charts. McConlogue says Grand's sudden success didn't come as a surprise. He worked hard and earned it.

Success - and friendship

Their story has propelled them to fame, with media around the world reporting on the pair. It's also cemented a rather unlikely friendship.

"The second day we met, one of the things I made very clear was that this was not like a charity. What we were doing, I said, is that we are shifting power from Silicon Valley to you. What you do with that is up to you," McConlogue says.

"He is just sprinting. He got the ball and now he's running."

And Grand wants to keep the ball rolling: He's already made plans for "Trees for Cars 2."

"If you are a driver with three or more passengers in your vehicle, you'll be able to pull up at any energy station and get a free gasoline card," he envisions.

Despite his success it doesn't seem he will be swapping the streets for a roof over his head any time soon. For now he's living in a tent.

"This is the thing. I don't consider myself homeless as an environmentalist. Truthfully speaking, it's more just me being eco-friendly."