If you have a margin acct you can transfer money from a bank into Fidelity and trade immediately, I can. The one limit is that you do purchase something with that money you can't sell that position until the money clears the next day. You have to transfer through Fidelity though and not your bank. If you go to transfer funds and set up a bank acct you can transfer from that acct to Fidelity!

I may add that you can sell the position I mentioned but will receive a good faith violation!