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Yes, but the way that works effectively is if the stock is low the day you buy it, then jumps up in value the next day and you sell at the high point. Then the stock has to drop again to a value where the profit from selling plus the fees for buying and selling the stock is slightly more than the stock plus the buying fee. Otherwise you lose money buying the stock.

That's called "day trading" basically ... in and out fast ... and most who do it lose money; its really making stock purchasing/selling more like gambling.

Remember also that you will not get long term capital gains, favorable tax treatment, if you don't hold it for 6 months, it will be ordinary income.

Yes of course you can do this, but remember if you are doing this then you must be aware about the market trend, so that you can be ready for the next day market opening.