Birds of a Feather - Guard Duty
Birds of a Feather is a decent quest to raise money for the credit check into New Vegas, even if you hate the Van Graffs. Note that they're a pretty good match up for evil characters (or just amoral characters), and it's a decent way to earn a lot of caps and get access to good equipment by the end.
Start the quest by going to the Van Graff store in Freeside. If it's your first time, you'll need to wait at the entrance until they're done with their “meeting." You should be able to start the quest by talking to Gloria Van Graff at the main counter. For your test, you'll be in charge of providing door security.
Make sure that you have some room in your inventory for a plasma rifle and metal armor. You'll have to put on their unique armor and use their energy weapon while you're on guard duty. You can pick between the laser rifle and the plasma rifle. Although, you don't exactly have to move that much, so you can probably just ignore the encumbered effects during the shift.
Just like your partner says, you need to keep out drunks and make sure that no one brings any weapons into the store.
The first guy is just a drunk, so turn him away. The second man should consent to the search just fine. The third man, the lucky gambler, will get indignant about the search. If you can't pass the Speech check you'll have to either turn him away or let him in. You'll lose your bonus either way, even though he's not a danger and won't consent without the check.
The fourth and final customer is the big decision, especially for people who want to take out the Van Graffs. His plan boils down to admitting that he has a magnum to try and get around the search. If you stand your ground, he'll panic and open fire. You shouldn't have any trouble turning him into a pile of plasma. He's got C4 on his body. Take it (C4's rare and expensive) and loot whatever else you want.
If you let him go, he'll go into the store and suicide bomb it with the C4. This will kill Gloria and Bastille along with all her guards. It will also destroy a fair bit of the inventory (which is worth a lot of money and one of the best sources of energy weapons, so think carefully about choosing this option), but it can take care of “Heartache by the Numbers" without any real pain. If you want to kill the Van Graffs, it's certainly an option. Note that letting this happen will turn the remaining Van Graff faction members, which should just include the door guard and the caller, hostile to you. Stay alert as you go through town and take them out when they attack.
Pacer should drop by, if he's still alive. Just talk to him and send him away. That should end your guard duty.
If you protected the store, just go in and report your successful guard shift to Gloria for 150 caps (200 if you passed the Speech check for the third guy).