Want to Become a Stock Market Millionaire? $250 a Month in This ETF Could Get You There.

There are many ways to become a millionaire through the stock market, and some are riskier than others. But if you have $10,000 to start and you can invest $250 monthly, you can get there in 30 years with minimized risk.

Beating the market

One of the lowest-risk ways to achieve millionaire status is by investing in an index fund that tracks the S&P 500. However, you'd need to invest a lot of money or wait a very long time.

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Instead, or in addition, you could invest in an exchange-traded fund (ETF) that tracks a growth index, like the Vanguard S&P 500 Growth ETF (NYSEMKT: VOOG). It's similar to the Vanguard S&P 500 ETF (NYSEMKT: VOO), but it focuses on the growth companies in the index. Instead of 500 holdings, it has 152. That's a riskier setup, but it's still well diversified.

Over time, that means it may be more susceptible to declines when the market falls, but it can gain much more when the market does well. And over many years, since bull markets tend to be much longer than bear markets, the growth ETF has outperformed.

Since inception in September 2010, VOOG has returned an annualized gain of 16.4%, edging out VOO's 14.8%, and it's actually the highest annualized gain since the inception of any Vanguard fund outside of two that were created last year.

Over a longer period, the S&P 500's annualized gain is around 10.9%, so let's assume a 12% annualized gain for the growth ETF over the next 30 years. If you start with $10,000 and add $250 per month, which amounts to a $3,000 annual investment, you'll have more than $1 million in 30 years.

Jennifer Saibil has positions in Vanguard Admiral Funds-Vanguard S&P 500 Growth ETF and Vanguard S&P 500 ETF. The Motley Fool has positions in and recommends Vanguard S&P 500 ETF. The Motley Fool has a disclosure policy.