Let's say that you deposit $10,000 in a margin account. Because you put up 50% of the purchase price, this means you have $20,000 worth of buying power. Then, if you buy $5,000 worth of stock, you still have $15,000 in buying power remaining. You have enough cash to cover this transaction and haven't tapped into your margin. You start borrowing the money only when you buy securities worth more than $10,000. This example applies to SPY, DIA, QQQQ However, in the same $10,000 account, if I applied the above numbers to the Proshares Ultra ETF's, would the numbers below be correct? $10,000 Margin Account $40,000 Buying Power If you buy $5000 worth of stock, you still have $35,000 in buying power remaining You start borrowing money only when you buy securities worth more than $20,000 Is this correct?