The easiest way to farm lots of caps in the early game is to kill Legion hit squads, loot their weapons, repair them between one another, and then sell them to a vendor.

Legion hit squads start to spawn at specific locations after the player reaches a Shunned reputation (or worse) with the Caesar’s Legion. They spawn in groups of 4.

Quick tips before you go hunt legion soldiers:

• You don’t lock yourself out of the Legion questline by doing this. As long as you do this trick before you finish the main story quest “Ring-A-Ding-Ding”, you will not lock yourself out of the legion questline. Once you’ve farmed up enough caps and XP, you can go do the main quest line and reset your Legion reputation.
• Prepare a powerful ranged weapon. The Legion often uses melee weapons like the Super Sledge, Thermic Lance, or the Machete. Having a ranged weapon enables you to kill them before they pose an issue.

Acquiring a Shunned Reputation

There are 2 places where you can easily and quickly find Legion soldiers to kill in the early game. Those are Nipton and the Legion Raid Camp.

Location 1: Nipton

Nelson is a town located east of the Nipton Road Reststop and North of the Mojave Drive-in (which is marked on your map as long as you own the Old World Blues DLC).

When you first enter the town, there will be several legion members, including a unique NPC called Vulpes Inculta, in front of the town hall. They are all heavily armed. Notably, Vulpes Inculta has a Ripper, which is a rare weapon in the early parts of the game. 

Simply kill the Legionnaires and you’ll have the reputation that you need. 

If you find killing them to be difficult, you can plant some Landmines and lure the legion soldiers onto them. You can also split the Legionnaires up by luring them around buildings.

If you want to use Landmines, there are 3 guaranteed-to-spawn ones that can be found near a wooden catwalk in Primm, which is the entrance from the temporary NCR camp there. 

Location 2: Legion Raid Camp

If the Legion soldiers have already left Nipton, your other, though more difficult option, is to attack the Legion Raid Camp, which is located south of Novac and West of the Broc Flower Cave.

This camp has a high number of Legion soldiers guarding it and it’s relatively open, meaning that it’s easier for the machete-wielding Legion soldiers to reach you, however, it also allows you to snipe them from afar using weapons like the .357 Magnum Repeater.

Legion XP and Bottlecap farm

The location where you’re going to be fighting the Legion hit squads is called El Dorado Gas & Service. It’s located by the road that leads north from Novac, and northeast of Helios One.

Once you’re there, go behind the gas station. You should see a Legion hit squad approaching you from a fair distance away. If you can’t, fast travel far away (like Goodsprings) and wait for 3 days, then come back.

Attack them first, they will turn hostile the moment they get close, so use the distance to your advantage.

Once they’re dead, pick up any valuable items (guns, Legion coins, food/water, or ammo). If you get any duplicate weapons, use them to repair each other, as that increases their value. 

If your HP is low and you aren’t playing on Hardcore mode, you can go back to the front of the gas station and sleep on the sleeping mat there.

Next, fast travel far away (like Goodsprings) and wait for 3 in-game days, then fast travel to El Dorado Gas & Service. The hit squad should spawn again, if not, repeat the steps again. 

If it stops spawning, you’ll have to go do something else for a while, as the hit squads appear to just stop spawning sometimes. 

Once your inventory is full, sell the items to a trader that is related to a faction that you have a high reputation with, as that increases the price at which the item will be sold.