Just put an order in to deposit funds into your account and robinhood allows you to use what you promise to pay them immediately, but it'll take that same amount of time after selling to get it back into your bank account. Just make sure not to use robinhood gold and click the box "use margins" because that's like a line of credit from robinhood that you're liable to pay for thousands if it goes in the red or something. I don't know enough about that but that's what i've read.