Finally, you can always invest small amounts in a k retirement account. The best practice to follow when thinking about investing in mutual funds is to begin before you invest any funds. Generally, stock mutual funds are appropriate for long-term periods more than 10 years ; bond funds are appropriate for intermediate-term periods five to 10 years , and money market funds are appropriate for short-term periods less than three years. This way you pay the trading fee just three times a year, rather than 12 times. Recommendation 1 : Save up the cash so that you can buy a Vanguard fund. Continue Reading.