You need, for sure, a bank account. For people living in the US they require a Social Security number, for tax purposes. From the time I was an alien (sic!), I remember that you had the option to pay taxes in other country, for earnings in the US. For these details you might contact online brokers who will tell exactly the requirements. You will need money, some stock market knowledge and/or a lot of luck.
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Bridge rule #1: Nobody is as good as he thinks about himself nor as dumb, as his partner thinks...