What's a 19-year-old multimillionaire pop star to do? If Justin Bieber is serious about "officially retiring" as he claimed in a Christmas Eve tweet, he'll need to answer that question in order to occupy all his newfound free time.

We're here to help. Since retirement can be a scary proposition at any age (and especially for a teenager who's made his life's fortune in the time it takes most kids his age to finish high school), MTV News has come up with a short list of possible second careers Justin should think about pursuing.

No Shirt, No Problem

We all know that the Biebs is practically allergic to fabric up top. But now that he's going to be spending way more time strolling along the beach and through the airport without a shirt on, what about launching a clothing line that caters to his quirky fashion sense? Teaming with fellow shirt shirker Matthew McConaughey, Bieber should totally launch a bottoms-only clothing line called JustPants.

Stamp Swag

You know what the kids are really into? Stamps. You know, those sticky things you put on that letter you send every year? Nothing says old-school philatelic swag like collecting something that only your grandma uses to mail in the bill for her AOL service. "Yo, have you seen those reissued Inverted Jenny stamps? Swag on a billion!"

First Bitcoin Billionaire

Speaking of billions, nothing says eccentric retired millionaire like starting a collection of invisible Internet cash that may or may not be the future of commerce.

Chillin' With His Homeboychicks

If you're loaded enough to bail early, there's only one place to go: Florida. Already considered an old soul by many, the Biebs should consider taking his shirt-allergic six-pack down to Miami Beach and taking advantage of the ample metal-detector-tolerant beaches, early-bird specials and killer domino clubs.

Turning Over A New Leaf

The kids love the fro-yo! If you've ever seen a group of kids piling their cup high with wedding cake/boysenberry and those weird fruit-juice-filled balls and Oreo crumbs, you know the real money's in by-the-ounce frozen yogurt.

Interior Design

We know from his extracurricular tagging that Justin has a keen eye for art and design. So, why not start his own interior design firm called, wait for it: JustInteriors. What would a Bieber-designed house look like? Owls and Tigers, lots of owls and tigers.

Turning The Tables On The Paparazzi

One reason Bieber suggested he was retiring was because of all the "lies" the media makes up about him. Now that he's got all that free time, why not start his own celeb rag that prints only good news about stars? The Bieber Beacon, alas, folds after three issues because, well, who wants to read only good news?