I would say call them and talk to them,  When I traded with Schwab, I could have a zero cash balance in my account, place an order to buy something, they would  fill it, and then I had 3 days to bring them the money to cover the trade.
Etrade is the best broker I have used.  Hooked it up to my checking acct.  I can click transfer money, it's done and available to buy with immediately.  It's a margin acct.