Hired Help

Recruit Charon is a minor quest in Fallout 3.

Accepting the Quest
If you speak to Ahzrukhal in The Ninth Circle in the ghoul town of Underworld, he will tell you that he holds the contract of employment (read: slavery) to a ghoul named Charon (also located in The Ninth Circle). Charon is bound to work for whomever holds his contract. Ahzrukhal also tells you that he dislikes having to compete with the other beverage outlet in Underworld, Carol's Place. He proposes that if you were to kill Greta, who works there, he would be willing to give you the contract to Charon.

Killing Greta
Remember that if anyone sees you kill Greta, they will become hostile to you, so the best time to kill her is when she goes on her smoking break just outside of Underworld in the Museum of History lobby area. She appears here around 9:00PM daily. Even if nobody witnesses you kill her, you will still receive Negative Karma.

Also if you have Mister Sandman perk you can easily kill her in sleep without getting any hostility from Underworld's ghouls.

Alternately you can simply buy Charon's contract with enough caps and you won't have to kill Greta.

Another method is to force Greta to attack you - thereby triggering the Underworld Residents to attack her in your defence (I used the mesmerizer in her sleep and she started shooting, then someone in the bar knifed her to death). This nets you NO negative karma or reactions from other NPCs, you can still raid Greta's body, and the contract will still be yours.

Another way to kill Greta is to use Robotics Expert on the Mr. Gutsy that patrols the Underworld. In the midst of conversation with the robot, those with the Robotic's Expert perk have the option to remove his combat inhibitor. This will cause him to go on a killing spree, attacking any nearby ghouls. It's up to you to make sure that Greta is nearby when you do this. One way is to rely on her smoking break. However, I found another solution. Talk to her when she's in bed. She'll get out of bed and start walking to you to converse. Before she talks to you, back up. Notice that Greta will keep walking towards you. You can now lead her anywhere you want. Now, all you have to do is lead her to the Mr. Gutsy, remove his combat inhibitor, and get the heck out of there. Once he terminates her, feel free to shut him down with a couple pulse grenades. You will receive no blame for her death in this situation, and I don't even think you will suffer a karma loss (not 100% sure on that).

Reward
After you murder Greta, return to Ahzrukhal to report your success. He will stick to his word and give you Charon's contract. After you tell Charon that you now have his contract, he will walk over to Ahzrukhal, who will think he's coming to say goodbye. Instead, Charon pulls out his shotgun and kills Ahzrukhal.

Bugs
Occasionally, when the player successfully receives Charon's contract and he is en route to 'bid Ahzrukhal adieu', Charon instead simply stands in one spot and is cannot be talked to, nor can Ahzrukhal. After this happens, Charon cannot be recruited and both will stand there indefinitely. The only fix is to reload a past save.

Charon will faithfully serve you regardless of your karma. You can have him carry items for you, shoot enemies, use melee attacks, and (surprisingly) use power armor, etc.

Cultural References
Continuing with the Greek Death theme of the Underworld, Charon (pronounced car-on), is the ferryman across the River Styx, which all dead souls must cross in order to get to Hades.