嗯，买他们自己的mutual fund的话，是没有fee的。但是这两家都有minimum investment requirement，Vanguard $1000，Fidelity $2500。就算到了minimum investment也还有个account management fee。必须投资总额高过一个限额才能免掉account management fee。所以在开这个account之前还是要先琢磨一下的。举Vanguard做个例子：

Vanguard Account fees

Index fund maintenance fee: Either $2.50 quarterly or $10 annually (depending on the fund), per fund account. Waived for index fund accounts with balances of $10,000 or greater.

Low balance fee: $10 a year per taxable, nonretirement fund account. Waived for fund accounts with a balance of greater than $2,500, or shareholders with total Vanguard fund account assets of $50,000 or greater.

IRA custodial fees: $10 a year per fund account with a balance of less than $5,000. Waived for shareholders with assets totaling $50,000 or more at Vanguard in any combination of accounts (retirement, nonretirement, employer-sponsored plan, brokerage, annuity).

实际上Fidelity和Vanguard都是mutual fund公司，不是broker。他们主要的收入不是account management或者trading commission，而是mutual fund expense。就是说你的钱放在mutual fund里面，每年他们会拿一部分走。具体是多少因mutual fund而异。一般在0.5%到2%之间吧。这个才是他们拿的大头。买mutual fund的时候别忘了要看这个哦。