Let's say that rather than peacefully settle next to you, he decides to take the fruits of your labor by threat (or use) of violence. Then, you either have to

Let's say that rather than peacefully settle next to you, he decides to take the fruits of your labor by threat (or use) of violence. Then, you either have to give up your wealth or focus on defense against violence instead of being industrious. Let's say you make an agreement that this neighbor that you'll give him food throughout the year in exchange for him repairing your infrastructure at the end of the harvest. If he takes the food but then doesn't help you when you need it, what do you do? You either have to fight him or cease dealing with him and absorb the loss. Either way you're worse off. Lets say your skill is canning and preserving food. Bartering with food producers is easy since you fill a mutual need with each other, but bartering with blacksmiths, bankers, and people that provide other services is much harder. You have to trade your services to people that value it less, or spend a lot more of your time to make arrangements. Any of which could be reneged on (see previous paragraph). Hence government monopoly on force, contract law, and currency. Three things we've had for so long that we forget they're there. Three (of many) intangible things that you gain increasing benefit from the wealthier you are. Warren Buffet, Bill Gates, or Michael Bloomberg would not have become billionaires living in the 1500s, nor if they were born in Zimbabwe (well, I guess they could have been trillionaires in Zimbabwe but you know what I mean).