In your 20s, you can invest dribs and drabs in the stock market and, through the wonders of compounding, become a millionaire by the time you retire.
Unfortunately, that strategy no longer works once you turn 70.
"The biggest challenge a 70-year-old has in getting rich is, obviously, time," Tilp says. "The younger you start, the easier it is."
To become rich after 70, you'll need to invest a lot of money each month, and pray for good returns.
James Twining, founder of Financial Plan in Bellingham, Washington, has run the numbers. He figures a 70-year-old starting with nothing would need to invest $2,393 a month at an annually compounded rate of 10% per year to earn a cool $1 million by age 85.
"The equity markets have, indeed, returned an average of 10% per year since 1926," he says. "So, it is not unreasonable."
Older investors wishing to get rich sooner may be tempted to gamble on high-stakes investing picks. But such a strategy actually decreases the odds of success, Twining says.
"The biggest challenge will be to resist the temptation to take risks by concentrating the portfolio -- attempting to pick winners or to time the market," he says.