Mutual funds may require an initial minimum amount when you’re first buying a fund, often $2,500 to $3,000. After that, you may need only modest amounts to continue investing in the fund. So it’s easier to continue buying into the fund with regular contributions.However, if you’re buying within a 401(k), those minimums are typically waived, and you can deposit whatever amount you want from each paycheck into the fund.Finally, it’s worth pointing out that some mutual funds charge a sales load, or commission, when you buy into the fund. These can be easily avoided by looking for “no load” mutual funds. The sales commission is money that should go into your pocket, not into the fund company’s.