0229 bieber
Canadian singer and actor Justin Bieber gestures as he arrives to attend the annual NRJ Music Awards ceremony on January 28, 2012 in Cannes, French Riviera. How will the star celebrate his 18th birthday? - 

Jeremy Hobson: Today one of the richest teenagers in the world turns 18. I'm talking about Justin Bieber, whose net worth is somewhere around $100 million. So when a child star becomes an adult star, what happens to the money? And to the star?

Sabri Ben-Achour went looking for answers.

Justin Bieber: I just need somebody to love.

Sabri Ben-Achour: Actually, Justin is going to need somebody to manage his finances. 

Susie Mains: A lot’s going to change for Justin Bieber when he turns 18 because he will have access to his money.

Susie Mains is talent agent who’s worked with young stars. Kids in showbiz, by law, have 15 precent of their earnings put into what’s called a Coogan account. Nobody can touch it except the star -- at age 18.

Mains: Sometimes it can actually show us who the child is.

Mains says it is no coincidence that some of the biggest celebrity meltdowns happen to child stars after they turn 18.

TJ Stein is also a longtime agent. He says:

TJ Stein: It depends on the families, it depends on how they were educated, and it depends on the kid.

For Justin and his millions, whatever happens, it’ll be one heck of a birthday party.

I’m Sabri Ben-Achour for Marketplace.