I never like to start playing a character at anything more than 1st Level because somehow the character doesn't feel "complete". I know this is silly because level is just a game mechanic and if you start, say, a 3rd level PC it just means you've got a bit more background to develope. Nevertheless, this is always how I've felt.
I'm the same when I GM. I rule that new players have to start at 1st Level. Admittedly, this does create some issues. For example, low level PCs will not get into "the thick of it" when I'm running an adventure for the high level characters. So far, however, it hasn't been a major problem.
At the moment, my game has PCs of quite varied levels yet we still have loads of fun. Their levels are: 19th; 16th; 11th; and 7th.
And I mean, look in the 1E Forgotten Realms box. In there they have lists of adventuring companies and the NPCs listed in each company have widely varying levels. These are NPCs, though, and I do understand that for player characters you should, ideally, keep there levels even so that each can equally "shine" in the game.
However, looking on the bright side: Due to the way XP is granted in 3E, the lower level PCs in my game are steadily catching up to the high levels.
