This guide tells you how to TECHNICALLY get unlimited caps.
How To Get Unlimited Caps, kind of.
So this is a very short guide and im pretty sure this is just a glitch. If you get Fisto at the atomic wrangler (you have to do a quest to get him), he will ask do you want to pay for my services. Say maybe later and you will get 10 caps. If you keep doing this for a while you can get a lot of caps but thats why I said kinda. He will never run out so this must be a glitch.