Quote from Susannah:
You just need to have enough for the liquidation value of your account to not go below the maintenance margin requirement. You'll have to figure out how many points you are willing to let it go. ES does lock limit after 5%, which they set every quarter I think, it was ~60 points the only time it's locked limit over night, but the limit is less now. I guess that would be the absolute most it could go against you overnight, the lock limit.
If you're trading with a small amount of money, you could just use SPY/SH and not have to short or use futures at all.
iv'e enver heard that before...what exactly does that mean? lock limit? does that mean should a position go against you that much that they liquidate part of position regardless of account ballance?