The only true way to make money doing this is with large sums of money and very high tech computers.

Some people, banks and other institutions have made money by finding gaps in currency exchanges over 10, 20, 30, 40 different trades. The amount made is small on a single dollar and not worth it. The gains on millions of dollars can be substantial. The information has to be gathered almost instantaneously so the cost of computers and software to do it can be expensive.

It's possible to make free money doing this but it takes a lot of money. You can make money holding different currencies against exchange rates but it more resembles the stock market.

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