Doubling the amount of money you earn from working would take a lot of effort. Most of us don't have that many hours in a day. But the beauty of investing is you can easily double your money (or more) without too much work, as long as you're patient.

Your primary goal as an investor is to grow the amount of money you start with into a much larger amount. But you also want to do so in a way that doesn't require more risk than you can stomach.

If you're looking to double your money, here are four proven ways to invest.

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1. Get your full 401(k) match

If your employer offers a company 401(k) match, taking full advantage is probably the easiest way to double your money. Many companies match your contributions dollar for dollar, up to a certain percentage of your salary.

For example, they may match 100% of your 401(k) contributions on up to 5% of your salary. In that scenario, you're doubling your money before it even gets invested, and it has the opportunity to grow even more. If your employer offers a smaller match -- say, 25% or 50% -- investing in your 401(k) is still a great way to double your money, even though it will take a bit longer.

Note that a 401(k) is a type of investment account, not an actual investment. You'll still need to decide how to invest the money. The average 401(k) plan offers between eight to 12 investment options. Two of the most common choices are mutual funds and target date funds.

2. Invest in the S&P 500 for the long haul

Another proven way to double your money over time is to invest in an S&P 500 index fund. These funds use the S&P 500 index as a benchmark and attempt to track its performance as closely as possible. The index is made up of 500 of the largest domestic stocks that together account for more than 80% of the U.S. stock market's value.

By investing in S&P 500 index funds, you're betting on the growth of the U.S. stock market. Historically, that's been a winning bet. In the 92-year period between 1928 and 2019, the S&P 500 index produced positive one-year returns 74% of the time. Over a 20-year holding period, S&P 500 returns have never been negative.

Had you invested in an S&P 500 index fund at rock bottom after the COVID-19 crash of March 2020, you would have doubled your money already. These results aren't typical, though. Average stock market returns are about 10% per year. At that rate, you could expect your initial investment to double in value in about seven years.

To invest in an S&P 500 fund, you'll need an investment account. If your 401(k) doesn't offer S&P 500 funds, you can invest using an individual retirement account (IRA) or a taxable brokerage account.

3. Become a long-term dividend investor

Your stock market profits come from two sources: You earn gains when you sell a stock for more than you paid for it, or you make money if you own stock in a company that rewards shareholders with dividend payments. Mature, stable companies are more likely to issue dividends, as faster-growing companies typically need to reinvest their extra cash in the business.

Doubling your money by focusing on dividend stocks will probably take a bit more time than if you invested across the stock market. But if you invest in a dividend mutual fund or exchange-traded fund, you can double your money in time, provided that you reinvest your dividends. 

The Vanguard High Dividend Yield ETF (NYSEMKT:VYM) and Schwab U.S. Dividend Equity ETF (NYSEMKT:SCHD) are two examples of funds that invest in stocks with a strong track record of paying out dividends and increasing them over time. A $10,000 investment in Vanguard's High Dividend Yield ETF made 10 years ago would be worth close to $34,000 today. The same investment in Schwab's U.S. Dividend Equity ETF would have soared to more than $40,000 in the past decade.

4. Buy and hold real estate

The average home price was up roughly 20% year over year, according to the S&P Case-Shiller U.S. National Home Price Index from August 2021. As with a lot of the investment returns we've seen since the start of the COVID-19 crisis, these results aren't typical. Over the past 30 years, home prices have increased by a little more than 4% annually. 

Whether these outsize real estate returns can continue is debatable. But given that the supply of homes is unlikely to catch up to demand in the foreseeable future, investing in real estate -- whether that means buying a personal residence or investment property -- seems like a solid way to double your money.

Don't buy real estate with the expectation that your property will increase twofold or threefold within a couple of years. However, even if property appreciation suddenly dropped to average levels of around 4%, you could expect to double your money in 15 to 20 years.

Want to double your money? Think long term

You may hear stories of people who became millionaires practically overnight by investing in things like penny stocks or Dogecoin (CRYPTO:DOGE). But these investments are highly risky. You're a lot more likely to lose most or all of your money than you are to get rich quickly.

Be skeptical of any investment that offers giant returns in a short period of time. Time and patience are the key ingredients in any proven method for doubling your money.

This article represents the opinion of the writer, who may disagree with the “official” recommendation position of a Motley Fool premium advisory service. We’re motley! Questioning an investing thesis -- even one of our own -- helps us all think critically about investing and make decisions that help us become smarter, happier, and richer.