Management fees, particularly those within Mutual Funds, can be very high (greater than 2.0% in some cases), which can seriously erode your investments over time. When I say erode, listen to this. A Mutual Fund costing you 2.0% compared with, say, an ETF costing you 0.5% will, assuming similar performance, result in a 40% reduction in your retirement savings over your working life. Mutual Funds will argue they provide superior performance, but it has been proven that less than 5% of these funds outperform the market once fees are considered. And when you check the fees, make sure to get the total fees because, in many instances, there are multiple different charges hidden in hard-to-find places.