Writing Fictional Characters

I recently returned from a marvelous vacation in Newfoundland where I encountered an incredible variety of extremely rich people. Someone in my writing circle (there are 6 of us, all writing fiction of various kinds) suggested they might be a great source for characters in my writing. My reaction was that I wasn't sure they would be. Since I am not part of that culture, I don't think I could write realistic dialogue, understand motivation for behaviour, etc for such creations. - Not unless I immerse myself in that culture for an extended period of time. Anyone willing to pay for me to spend a few years there?

That started me thinking about the whole issue of creating realistic characters. One of the maxims of writing is to write about what you know. So how divergent from ourselves can those characters be? For example, I think I can create a character who is mean, insensitive, and macho in a negative way, and that is all very unlike me. But I'm not sure that I could create that character in other than a stereotypical way if he was to come from the inner city of a large metropolitan area, something I am not familiar with. (I have never lived in a large city.)

Any comments? When you create characters, how do you do it if they are quite outside your culture or experience?