I don't have a margin account. I tried doing this, sold, then bought back in, then sold again. Didn't do too bad. Problem is that was my total funds, so then I got a Regulation T restriction Email.
Said if I paid them the price of buying the stock in full by 3 days(sounds like a bookie) then I'm okey. Which is pretty super stupid in my opinion, as I had to pay by the day the funds settled anyway, so now I have more money in the account.
If you have a margin account, no problem I understand. If you have enough money, where you had the buying power in the first place without the flip, you'd have no problem. It's when you use the same dollar bill over and over that you're going to run into trouble.