Well, maybe it doesn't happen in US, but it happens quite often in Brazil. There is lots of people who were dirt poor in their childhood but were smart and worked hard and ended up rich. My grandfather was like that, he was from a really poor family that couldn't even afford to send him to school, but he learned math by himself, built a store (it was both a bar and a store, and he had some interesting tricks to keep the customers for very long, and the longer they stay, the more they consume) and that turned him into the richest person in his town for some time.
But like a famous phrase in brazil says: "dinheiro na mão é vendaval" money in hand goes away like the wind.