Selco’s course gave me a lot of insight on how to deal with trades. In SHTF… everything will be the black market… and everyone you buy from is a potential thief at best, murderer at worst. Including people you ‘thought you knew.” Only your most trusted (typically family, maybe neighbors and best friends) associates will be actually trustworthy. Everyone else you should assume potentially dangerous. Statistics show that upwards of 11% of all people have latent sociopathic tendencies that will be not so latent once society breaks down. (I believe that’s somewhere in this forum, too).
It goes without saying that you should be armed when trading/buying.
Rule 1 is not to appear ‘weak.’ Let your stance, tone, armament, etc. demonstrate that you’re not somebody who should be messed with.
Rule 2 is not to be too tough, because some people will target you to gain fear/respect in the area. Rule 3 is to keep transactions quick and simple; the less time you spend in their presence, the better.
Rule 4 would be to never allow them to know if you need something badly. If they know you’re desperate, they’ll make you pay dearly.
Rule 5 is to never reveal to a buyer/seller anything about yourself or your group (and is a good general rule.)
That’s kind of my quick and basic breakdown. Prices will be something you learn on the go, too hard to predict what things will be truly worth until the SHTF.