I don’t think Steven was taking any drugs at all. I also don’t think he was passing out flyers. I think his landlord was into something shady/illegal and asked Steven to either pick up or deliver something to help cover the rent he owed. Steven may not have even known what it was. He most likely wound up in the wrong place at the wrong time or ran into some bad people.
If Steven agreed to deliver something for his land lord to make up for back rent, then why was the landlord calling Steven's parents about the back rent? If he and Steven had an agreement about doing errands to make up for back rent, then calling parents about late rent isn't necessary.