If the mutual fund you invest in is a no-load fund, then the only cost of investing can be found by looking up the expense ratio. This is a percentage of the fund that the company keeps as payment for managing the fund. In general, actively managed funds have higher expense ratios than passively managed index funds, and in general, they range from 0.015% to 1% or more. Some mutual funds also have sales loads that are charged when buying or selling shares (depending on their structure). Keep in mind that your brokerage may also charge you fees associated with buying or selling mutual fund shares.