It looks mostly like a cash, hand to hand type thing.

I'm not sure how it works exactly but if I had to guess, it looks like one of them takes the money and they get the drugs from someone/somewhere else. I think they might use unhoused people to hold the drugs so that there's plausible deniability and separation of concerns. For the last few months, it looks like they're using an obese man because they know he literally can't run away with their drugs.