(A/N: Discord link: discord.gg/SC9HNKVj5e )
Li Huang might not be a genius, but he is not an idiot. The idea to sell drugs was something that he knew would work for sure. In a word of cultivation and body refinement, many of the addictive and harmful drugs from his past life would be considered elixirs of mental clarity and miracle pills that make advancement in cultivation much easier.
It also wouldn't be like a cultivator would face much of the negative effects of those drugs, and even if they were affected by it, it wouldn't be much worse than the pills that the cultivation world uses right now. You can also simply blame those effects on mortals, on the simple fact that their bodies are weak and fragile. Well, not that they could afford the medicine meant for cultivators in the first place.