I trade with lower-ranked people all the time and I've never had any issues with them. Most of them realize that they're not in the place to be demanding others go first.. at least with me. I'm pretty sure most people here judge by your personality/maturity more than your join date.. unless you're in the spam forum. In the black market, all you have to do to be taken seriously is to take the trade seriously, don't create ridiculous demands you know you wouldn't comply with if the roles were reversed, and be mature.