Presumably 1,000 with a large modifier with wins/losses for the first games. If you get an ‘accidental’ win (like from a d/c or dodge) in your first 2-3 games and get +150 elo it can seriously screw you up - you might have to lose 5 games to get back down to your proper level.
Interesting. I was wondering why I started with 1,100. I thought it would start at 1,200 for some reason.
I won the first four games, then faced a bunch of nasty rushers, heh.