As far as I know Bitcoin started evolving after the huge success of Silk Road (
https://en.wikipedia.org/wiki/Silk_Road_(marketplace)).
Be extremely careful if you set a black market. The first clients can be secret service agents. They can come with hundreds of
BTC and become your friends. Few month later you can be in a prison

.
You will only be in prison if you are doing something illegal, which is why most people explore the dark web anyway. I wonder who invented it in the first place

Yep so thats why its quite dangerous selling something, they'll fake that they buy something and then before you know it your getting swatted in front of your house lol
if you're selling in illegal website than you must selling an illegal stuff and you're know the risk of selling it so there's no different between selling in a legal place or illegal because you're selling the same stuff that's illegal,both could drive you to be prisoned,and if you're selling legal stuff then why bother to sell it in illegal marketplace?
Indeed selling illegal goods is something that is not good in our lives, otherwise we can't get a good thing for sure we are going to deal with the police. Because the items that we sell are contrary to applicable law. Don't ever do this, if you do not want your life become a bad thing