Just over a year ago, Charlie Puth was a Berklee College of Music grad living at home with his parents in New Jersey. Now, at 24, he's one of the world's fastest-rising pop singer-songwriters, with a gated house in the Hollywood Hills, Grammy and Golden Globe nominations and a hit -- Wiz Khalifa's "See You Again" -- that spent 12 weeks at No. 1 on the Billboard Hot 100 in 2015. "It has all happened stupid fast," he says with a chuckle. Today Puth is in New York after a late night with his new buddy Selena Gomez, cutting a song for his debut album, Nine Track Mind, out Jan. 29.