If you use the proper websites for your purchases, via TOR, you'll find that there actually exist rating systems that can already tell you a lot regarding the t

If you use the proper websites for your purchases, via TOR, you'll find that there actually exist rating systems that can already tell you a lot regarding the trust you can have in a specific vendor (if you spend a couple of minutes thinking about how the given rating system works and if you take the numbers into account - hint: you need big numbers). The second step will be an LSD test you can buy online on conventional websites. Never buy on the street - those people have absolutely not reputation to lose.