It depends who your trustee is & the structure. I've been the trustee for 5 trusts so far, & haven't charged the trust a managerial fee because the beneficiary is family. Each trust requires its own tax ID number & a Form 1041 each year. The taxation amount depends on how the trust assets are invested & when they have to be distributed; I used tax efficient investments like no load index funds which compounded over the years. In a trust like this, any taxes due are paid by the trust each year & then trust disbursements get paid on behalf of the beneficiary tax free. All of these trusts were for growing an initial investment for education, to be cashed out to the beneficiary by a specified age if that person didn't go to college or trade school or didn't need all of the funds.
For trusts with large assets & complex requirements, you do want an investment bank as trustee. Here is where you can expect the trust to pay an annual fee, usually 1-2%. The bank controls the trust but it's a good idea to give the beneficiary the power to change the trustee to another bank.
Legal fees to set this up depend on the complexity of what you want. You also need advice on estate taxes depending on how you structure things.