to knock or not to knock?

I had a busy day of services today,  I continued to come across an issue.  I would ring the doorbell and wait for an answer. I waited to what I thought it was long enough. Then I would knock, at which point they would answer the door.  Several of them were a little frustrated with me, I think.  Here is the Dilemma, how long do you wait for someone to answer the door before you attempt another way of getting a hold of them when you know that they are home?  One guy would only open his door like two inches,  just enough to see one and half eyes. I am not a bad guy just the bug girl to kill your bugs buddy...

I was going to a friends apartment to get a key to get into my apartment, we haven't made extras yet. I see this kid in the parking lot starring at me.  I ignored him as I got out to the truck, he didn't ignore me.  He asked if I knew someone. I had no idea who he was talking about, I started walking to the apartment he then asked me if I wanted to go smoke something.  I don't know exactly but I think that it was something close to Marijuana.  I turned around and said What? He pulled up his hand and said you wanna smoke? I turned back around and said NO, no thank you! I was proud of myself for not even thinking about how I was to respond. But I was in shock. I am still in shock.  I really am frazzled over it,  I don't know what to do with myself. I think it is because it was in his hands in a bag. He was walking around like there is nothing wrong.  For him there is nothing wrong, for me there absolutely is.  

One crazy day....only more to come, I'm sure.