Zax will offer four bounties. The usual reward for a complete bounty is 300 credits; however, a player with a high persuade skill can persuade him to raise the reward to 400 credits. Note that this persuade check must be made each time the PC talks to Zax to collect each individual bounty.
Selven is an infamous assassin who wiped out an entire noble family on Taris. While it is never officially known which rival family hired her, one of the noble families has decided she is too dangerous to allow to live and has set a bounty on her head. As a feared assassin, this bounty is considered "legal" and will not affect your moral standing in anyway; Carth will have no objection to it, either. However, Selven is quite formidable and has killed all other bounty hunters who've tried to take her on.
Dia is a waitress who stabbed one of Davik's men, Holdan, when he got fresh with her. Furious over the loss of face, Holdan has put a bounty on her. If you explored the apartment level you first started in, you should recognize her as your next door neighbor. Carth will find this bounty morally objectionable and will try to talk the PC out of it should you decide to complete the job. Dia will also attempt to make a deal with you to get Holdan to call off the bounty. Killing Dia will result in Dark Side points, whereas aiding Dia and refusing her reward will net you Light Side points.
Matrik once worked for Davik, but eventually turned state's evidence against the crime lord and going into witness protection. Davik lost a lot of credits and contacts putting things back on track, and has declared Matrik's life forfeit. Since the Sith have invaded, however, the witness protection program has dissolved and he is hiding out in the Lower East City Apartments. Carth will also not approve of this bounty. You can decide whether to earn Light Side points by helping to fake his death and still collect on the bounty, or simply kill him. If you want to avoid some dialog and moral choices, when you break into his apartment, tell him you're here to rob the place. He'll attack, you and Carth will defeat him, and you can loot his footlocker. Note that if you take this third option, you will not net any Dark Side points for killing him.
Largo was a merchant who couldn't pay his debts to Davik and now you get to decide what to do about it. If you explored the other apartments in the same block as the Sith party or the Sith interrogation, you likely ran into Largo already. If you chose to extort money from him in exchange not to tell Davith's men where he's hiding, then after taking his bounty you again try to extort money from him, he'll tell you he hasn't got any more money, at which point you can tell him he can tell that to Davith's men and he'll attack you. In this way you can kill him without being presented the choice to help him or ruthlessly murder him. If you help him, you will net Light Side points; if you kill him, you net Dark Side points. Note that if you took the extortion route and killed him "out of self-defense", you will not net any Dark Side points for killing him.
Zax has some limited information available to your character...for a price. He will charge you a one-time fee of 100 credits; if your persuade skill is high enough, he can be talked down to only 50 credits. He will offer you information on Davik, the Lower City gangs, getting off-world, and a recommendation to talk to the Hidden Bek gang if you want to get into the Black Vulkars' base.