i dont seem to have that problem with my Etrade(they are very relaxed on penny stocks) account as long as i didnt get it locked down for trading unsettled funds, i can quick transfer direct from my back account to my broker account and the money is cleared for buying instantly but not settled so i would get locked if i was to complete a trade with those funds till after the 3 day period

now i have not not tried that with large sums of cash so maybe there is a cap on how much they can clear instantly but i haven't found it yet

also i think there might be a rule that depends on how much money you have in the market or cleared in your account compared to the money getting deposited