Nothing illegal about that trading tactic. Also, as someone stated, most trade execution platforms has a button that allows you to do all that in one click (buy the sell) or (sell then buy)....you'll see that button sometimes called "position reversal", "trade reversal", "buy/sell", "sell/buy" and many other short names depending upon the platform. It's a tactic used mainly by daytraders, scalpers and automated trading systems. You'll generate (pay) more commissions to your broker and that will make your broker very happy although your account will shrink if your profits is not greater than your commissions. This is why we as traders need to spend time learning our trade execution platform so that we know what all the buttons are (their function) prior to any real money trades. If you don't know (didn't feel like learning them)...just call the tech department of your software but most platforms have a operation guide that your can download and read... Some even have online videos at the broker website. Generate enough money to your broker via doing such type of position reversals...you may even get a Christmas card from the broker during Christmas.
Any trading has risk with any account level, amateur or not. In any case, you need $25k minimum in your account to day trade because of US regulations. For the details of the regulations, read about pattern day trading/trader (PDT) rules.
ok thanks guys, you guys answered my question, i am no longer scared to try it out. And i am aware of the PDT rule. thanks again guys.
It appears you are new at trading so you need to be aware of the wash sale rule since it is doubtful if all of your transactions will be profitable.