The "I don't make any money - I do it for the children !!!!!1!!!!111111" argument..
Although I cannot verify this as its a violation of privacy - I can say as a letter carrier that one learns many things about the people on the route through osmosis. And because I see the monthly NEA union mailings, I know where the teachers live. And they are in the best neighborhoods, and in some of the most expensive homes on the route. They live in the same neighborhoods where the doctors and lawyers live.
Again, I will never verify any of this to anyone - so you can decide on your own if I am being honest.