So on brokers like etrade, optionshouse and sogotrade you need a minimum of $2,0000, this is I know.

 

However, lets say you only have $2,0000 on the account, can you be able to trade with those funds, because if you place a trade, you're using some of the $2,000 thus being below the margin requirement. soooo do they buy you in? Can someone clarify this to me?