Bruno Mars and Travie McCoy's hit single "Billionaire" might have never been written had Mars been aware of the exchange rate between the U.S. dollar and British pound.

According to Mars, he came up with the hook to the pop-rap hit last year while walking around London and slowly realizing just how broke he actually was.

"Me and [production partner] Ari Levine went out to London to work on producing and writing for an artist. We had per diems, so they gave us £250 [a few hundred dollars] each to live off of for 11 days," Mars says. "And everything there was so expensive. We were like, 'Is this the biggest mistake we've ever made? We thought we were broke in California; what are we going to do here?' So we've got no money, and I'm walking the streets and came up with, 'I wanna be a billionaire, so frickin' bad.' "

Mars might have been strapped for cash, but the 24-year-old Hawaii native was already impacting pop radio as a member of production team the Smeezingtons before the "Billionaire" refrain popped into his head. Mars' featured vocals on the song's chorus, as well as on B.o.B's Billboard Hot 100-topping "Nothin' on You," were preceded by a songwriting credit on Flo Rida's "Right Round" and production work on K'naan's "Wavin' Flag," which became the 2010 World Cup's official anthem.

Yet for Mars (real name: Peter Hernandez), it's never been about producing other people. Although he was hawking his Smeezingtons material to pay his bills, Mars' focus remained on his solo career.

On the eve of the Oct. 5 release of Mars' stylish debut album, "Doo-Wops & Hooligans," Elektra co-president John Janick thinks that the success of "Nothin' on You" and "Billionaire," as well as the steady growth of the disc's retro-romantic first single, "Just the Way You Are," have set up Mars as a multifaceted flagship artist for the recently revived label.

Bruno Mars Stays Atop Hot 100

"We were thinking that, if all these songs were hits, it will help him develop as an artist before his first album," Janick says. "It came together exactly right. The songs introduced his voice to a lot of different people."

YOUTH IN REVOLT

After spending his childhood onstage performing doo-wop songs with his father in Hawaii, Mars graduated high school at 17 and flew to Los Angeles to start a solo career. His older sister had a connection that landed Mars a deal with Universal Motown, but Mars says the relationship was "more of a 'sign a kid who can sing and see what happens' " partnership, and Motown soon dropped the singer after studio time yielded disappointing results.

While Mars chalks up the failed deal to his own inexperience, he was more dissuaded by the process of "bouncing around from producer to producer" and struggling to find one that understood his songwriting ideas.

"He was clearly talented, but there was no control as to where he was going," says Philip Lawrence, a songwriter who gelled with Mars at Motown.

When Lawrence realized that Mars was a seasoned guitarist, bassist, pianist and percussionist, he suggested that the two of them begin creating their own backing music and start producing on the fly. The two dubbed themselves the Smeezingtons-a riff on the word "smash"-while later adding Levine as an engineer.

Suddenly Mars had a team behind his music. With no one answering his calls, however, he still didn't have any money. A record label eventually reached out to Mars, but instead of giving him the deal he needed, it asked to use one of his songs for another artist.

Mars recalls, " 'We said, 'No, absolutely not. This is my art.' They said, 'We'll pay you a lot of money.' So we said, 'OK, here you go, have it.'

"It was either that, or I was going back to Hawaii," he continues. "After we sold the first track, it opened our eyes. We put the artist stuff on the back burner and took some of the pressure off ourselves."

Next: Mars Hits No. 1 Days After Being Arrested