Now that's a shady figure you wouldn't want to meet in a dark alley. Or maybe you do. He's actually quite pleasant if you get to know him, if you catch my drift...
The drug dealer is the shady type of villager who will try to sell you illicit and rare substances if you're able to find him. You will normally encounter them in villages tending to his secret farm. These villagers use the drying table as their workstation and will carry out the normal routine of farmers, gathering crops and using the drying table to dry them to restore their trades.
Trading GUI (prior to 1.6.0)