With this sort of contract, the owner of a big, highly appreciated stock position gets an upfront payment from an investment firm--typically for 75% to 85% of the value of his shares--in exchange for agreeing to deliver a variable number of shares or cash in the future, with the exact amount dependent on how the stock performs.

FORBES: Billionaires' Taxes

That is because there is no natural income flow, unlike with bonds, in which investors receive a regular interest payment, said Thomas Kressin, who heads currency strategy for Pacific Investment Management Co. from Munich.

WSJ: Strong Start to 2013 Hints at Revival for Currency Funds

Eight years later, I sold it at more than double my investment, and then used the profit as a down payment for a larger home, where I still live today.

FORBES: How I Transformed My Finances After 30