Tend to Your Business

 is a quest in Fallout: New Vegas.

After replacing the Brotherhood Elder with Head Paladin Hardin, he will ask you to go to Freeside and kill all the Van Graffs and their men to prove your loyalty.

Quick Walkthrough

 * If the player has not yet completed Birds of a Feather, ask Gloria if she has any work. She will assign the player work as a door guard. Allow the fourth 'Gambler' to approach the door (saying he wants to replace his Revolver) to enter, saying that since he "declared his weapon, he's good to go". He is actually a suicide bomber, and will kill everyone inside the Silver Rush once allowed in.

Detailed Walkthrough
The easiest way to complete this is to set C-4 Explosives down at the feet of each person in the Silver Rush. Since they aren't hostile to you, they will stay in place despite this. Then simply head to the bathroom, well outside the blast radius, and set the C-4 off with the Detonator.

An even easier way is to ask Gloria if she has any work for you. She will assign you work as a door guard. The fourth 'Gambler' to approach the door will say that he wants to replace his Revolver. Let him in, saying that, since he declared his weapon, he's good to go. He is actually a suicide bomber, and will kill everyone inside the Silver Rush if you let him in.

You can kill them all during the botched arms deal to the Legion, then go back kill the doorman and all the Van Graffs have been killed, now go back to the brotherhood bunker and the quest is complete.

With a sniper rifle modded with the suppressor equipped, find an area where you are 'hidden' while sneaking, and hit the guards in the head for a one shot kill, that leaves the others unaware. Attacking any named character in this manner will cause all factions members to be hostile toward you, so make sure to kill the guards before you target Van Graffs or Simon.

There is a "dead spot" behind the pool tables where you can sit and hide. So with the Incinerator burn them up and run behind the table. Enemies can shoot but they will hit the table and you can still burn them with Incinerator.


 * It is also possible to draw all the guards out into the streets of Freeside. setup Plasma mines by the car just before the Silver Rush. Kill the rush Crier first as he will become hostile.  Shoot the door guard with a non silenced weapon and stand 3-4 guards will join from the Silver Rush. Use a powerful rifle as the Van Graff guards are tough AP ammo works decently well. If you have it, the Archimedes works fantastic here. Once guards are all dead, enter the Silver Rush crouched. Pop a Stealth Boy throw a few Plasma Grenades. One guard and the two Van Graffs were left inside use a sniper rifle silenced they do fire back, but are confused for a time.*

It is also possible to draw all the guards out into the streets of freeside and make them follow you and enter the strip and wait for them to enter the strip. Then enter the lucky 38 and they will follow and as soon as they enter the securitrons will shoot them (i already had them upgraded to the mark II so they were using their rockets.) Then you go back and kill gloria and the other guy in the store. (No longer possible in patched version of the game, securitrons will remain neutral to the guards even when they're shooting at you inside the Lucky 38 casino)

Another technique is to use a Stealth Boy while out of sight in freeside, then enter the Silver Rush and crouch. Once inside and sneaking, go up to the main characters, when you are prompted to pickpocket them plant a frag grenade and immediately start backing up. This will kill them and you can move away from the responding guards to stay hidden. If you have a problem with this, you can run in the back and upstairs out of sight and use another Stealth Boy to escape detection.

Either one of those above or just walk in, kill them and walk out. Simple

Bugs

 * If you have already killed the Van Graffs before receiving this quest (such as through Cass' companion quest) it will be impossible to complete by normal means; the game will merely direct you to the Silver Rush. However, this can be fixed by opening the console and typing 'setstage 1633f2 20' (sans quotes). This will mark you as having killed the Van Graffs, and you will be able to talk to Hardin and complete the quest.
 * Just adding to this bug, try leaving L2 of the Bunker then re-entering, the option came up after.
 * If leaving and re-entering does not work, try opening and closing your pip-boy.