Real Productions casts amateur guys in their films all the time. I wouldn't consider any of them "porn stars," or even on their way to being a "porn star," as Robbie hit the nail on the head with that. But, for someone looking to break into the industry, Real Productions might be one of the best ways to go. They have a site called
AverageJoesXXX.com which puts aspiring male talent on a list to be auditioned when Real Productions rolls into a nearby town to shoot something. The site is featured prominently on the show "The Boy Nexxt Door" on Playboy TV.
From what I've gathered from talking to Jason, the President of Real Productions, a guy pays a $10 fee quarterly to get access to a list of upcoming shoots from Real Productions. When they see something in their area, they apply for an audition using a special talent ID number they receive for being a member of the site. Then they wait for the call, show up to the audition, and hopefully get to bang some chicks. I think the guys do get paid for the film role (if they get cast, of course), too, but I'm not 100% sure on that.