People often ask celebrities for autographs, but not all of those people are fans. ET went inside the world of autograph hounds who turn memorabilia for profit.
NEWS: 7 Selfies With Celebs That Prove the Autograph Is Dead
"I've made several million dollars in this industry," Autograph Pros. founder Michael Kasmar told ET.
The profitability of the business has led some celebrities to be more hesitant to sign autographs. Pitch Perfect star Rebel Wilson sent a clear message to those looking to capitalize on her signature through a tweet, asking professional autograph hunters to "stop stalking [her]."
"I'm not signing your pics that you sell online," she wrote.
NEWS: Demi Lovato Says Her Gynecologist Asked for an Autograph
Rebel later explained the move to ET, saying, "We're here for the real fans not the ones that are trying to make money by selling our stuff."
A signature from Rebel can go for as much as $70, which is a solid payday for a scribble on a piece of paper, but pales in comparison to other celebs. An autograph from Mick Jagger could net up to $2,500!
"Getting Mick Jagger to sign anything is nearly impossible unless you're a female and have good looks," Michael explained.
As it's unlikely to bag a whale like Jagger, making a career out of the autograph business takes strategy. For Tyler Manninen in New York, it's all about patience.
NEWS: How James Brown Inspired Mick Jagger in Music
Tyler waited outside for hours to get an autograph from Sarah Jessica Parker after her appearance on Late Show With David Letterman.
For Giovanni Arnold, the key is to always be prepared.
"I've got my microphone, my baseballs, my photos and glossy paper," Giovanni told ET, going through his bag of swag.
NEWS: Rebel Wilson Thinks 'Bigger Girls Do Better In Comedy'
Watch the video to see what Giovanni went home with after a pre-Met Gala event.