I was a paperboy as a kid and went door to door on every Saturday morning to collect $$ for the week. I would knock and shout "Paperboy!", so I never came as a surprise. Most people were dressed but some were always in various states of undress. The few naked ones, 1 or 2 women, generally didn't open the door all the way. Just wide enough to see out, say g'mornin', and hand some money out the door. That was a long time ago but the only concern I remember was making sure I could make correct change for everyone. Maybe it was no biggie because, on Saturday morning, who would expect everyone to be dressed? It never occurred to me that it could be an issue. I just wanted to get finished and get on with my day. Now that I think about it, any delivery guy who even notices how people are dressed (or not) is probably not well suited for that line of work. On the other hand, I don't recommend exposing oneself to a stranger unnecessarily either. It's just not a good idea.