Being Charlie stars Nick Robinson as Charlie, the son of a famous former actor running for governor (Cary Elwes). "It's not my life," says Reiner of the film, but "I went to a lot of these places, so I had a lot of these stories."
One thing Charlie faces briefly in the film is homelessness, something with which Nick had significantly more experience. "I was homeless in Maine. I was homeless in New Jersey. I was homeless in Texas," recalls Nick in his father's West Hollywood office. "I spent nights on the street. I spent weeks on the street. It was not fun."
Courtesy Michele Reiner
Nick's sojourn on the streets and in and out of shelters came after he refused to go back to rehab. "If I wanted to do it my way and not go to the programs they were suggesting, then I had to be homeless," he says.
For more about Nick and his battle with drug addiction in one of Hollywood's most famous families, pick up the latest issue of PEOPLE, on newsstands Friday
But that experienced proved valuable, he concedes, and not just in writing the film. "That made me who I am now, having to deal with that stuff," he says. "I met crazy great people there, so out of my element. Now, I've been home for a really long time, and I've sort of gotten acclimated back to being in L.A. and being around my family. But there was a lot of dark years there."
Since leaving his last rehab facility at 19, Nick has been working on the film, writing other projects and trying to stay clean so that he never goes back to the streets again. "When I was out there, I could've died. It's all luck. You roll the dice and you hope you make it."
Being Charlie opens May 6.