Rock of Ages

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In 1987, Sherrie Christian (Julianne Hough) arrives in Los Angeles from Oklahoma with dreams of becoming a singer. Meanwhile, barback Drew Boley (Diego Boneta) prepares for another night of work at The Bourbon Room ("Sister Christian/Just Like Paradise/Nothin' But a Good Time"). As Sherrie approaches The Bourbon, her suitcase is stolen. Drew tries to catch the robber, but fails. He comforts Sherrie and, upon learning of her situation, gets her a job at the Bourbon Room as a waitress.
The club's owner, Dennis Dupree (Alec Baldwin), and his right-hand man, Lonny Barnett (Russell Brand), are trying to find a way to pay off a tax debt that threatens the club. Hoping to raise enough money, Dennis and Lonny decide to book Stacee Jaxx (Tom Cruise), a detached and self-indulgent rock star preparing for his final gig with his band, Arsenal. That night, Drew tells Sherrie about his dreams of becoming a rock star, but that he has stagefright ("Juke Box Hero/I Love Rock 'n' Roll"). Upon hearing of Stacee's upcoming concert, Patricia Whitmore (Catherine Zeta-Jones), the religiously conservative wife of the mayor (Bryan Cranston), organizes a protest with other ladies in front of the Bourbon Room ("Hit Me with Your Best Shot")
Drew and Sherrie's relationship starts with their first date at the Hollywood Sign where Drew admits he has started writing a song for Sherrie ("Waiting for a Girl Like You"). On the night of Arsenal's final show, Dennis learns that their opening act has cancelled. Sherrie convinces him to use Drew and his band, Wolfgang Von Colt, as the replacement opener ("More Than Words/Heaven"). Meanwhile, Stacee's manager, Paul Gill (Paul Giamatti), schedules an interview between Stacee and Constance Sack (Malin Ãkerman), a reporter for Rolling Stone.
During the interview, she mentions the rumors that Stacee is difficult to work with and implies that he was actually kicked out of Arsenal, a charge Stacee denies ("Wanted Dead or Alive"). Stacee asks Sherrie if she could bring him a bottle of scotch from his limo and she agrees. After the interview, Constance lashes out at him, claiming that he was once a great musician but now is on the verge of becoming a has-been. Stacee orders everyone out of the dressing room so he can settle things with Constance privately. Both recognize their love for each other and are about to have sex when Stacee sings ("I Want to Know What Love Is"). As Constance leaves the room ashamed of what she has done, Sherrie enters to give Stacee his scotch. Sherrie and Stacee collide and the bottle of scotch shatters on the floor. Drew is getting ready to open Arsenal's show when he sees Sherrie exit Stacee's room, where he infers that they had sex. Drew becomes angry at this and is inspired to sing ("I Wanna Rock") for the opening act. After he sings, Drew and Sherrie break up and Sherrie quits her job at the Bourbon Room. Drew attempts to run after Sherrie but Paul tells him to let her go and offers Drew a record deal since he was impressed with his performance as Arsenal sings their last song of the night ("Pour Some Sugar on Me").
An unemployed Sherrie takes refuge at a strip club bar known as the Venus Club, where she has no other choice but to work there ("Here I Go Again"). Drew is disappointed in realizing that he has to be part of a boy band called "the Z Guyeezz" and not a rock band as part of his record deal ("Any Way You Want It").
Sherrie visits the Hollywood sign, where she finds Drew. Sherrie tells Drew that she didn't have sex with Stacee and that she is going home. She also admits that she has been working as a stripper. Drew admits his new act is actually a boy band. Sherrie and Drew both lament the situation. Meanwhile, Dennis and Lonny realize their love for each other ("Can't Fight This Feeling").
Stacee realizes he has feelings for Constance and calls the Rolling Stone office in an attempt to find her, but the receptionist tells him that "she is covering Stacee Jaxx's show at The Bourbon Room" and Stacee, unaware that he was supposed to perform that night, rushes to the venue, where Lonny leads the patrons of the club against Patricia and her protest group ("We're Not Gonna Take It/We Built This City"). When Stacee arrives at the club, he recognizes Patricia, and Lonny discovers that Patricia was once a groupie for Arsenal, and exposes this to the public, ruining her reputation. Meanwhile, Drew has found all of Sherrieâs stolen records at the Tower Records they first visited together. He buys them back and drops them off for her at the strip club.
The Z Guyeezz start the show, but the rocker crowd rejects them, and Drew, spotting Sherrie in the audience, leaves the stage. The two reconcile and Drew also dismisses Gill, who is then punched in the face by Stacee's pet monkey Hey-man. Sherrie reunites Wolfgang Von Colt for the opening act, where she and Drew perform the song he wrote for her ("Don't Stop Believin'"). Stacee hears the song and is moved by it.
Eight months later, Stacee, who has rejoined Arsenal, performs the song with Drew and Sherrie, who is now part of Wolfgang Von Colt, in a concert at Dodger Stadium in front of a crowd that includes Dennis, Lonny, Justice, a pregnant Constance, and Patricia, who has returned to her rock 'n' roll persona.

Question: Why are Dennis Dupree and Lonny Barnett trying to raise money?
Answer: To pay a tax debt.