cvds, if you are only managing 1 guys account you can open a brokerage anywhere in that guy's name and set up a power of attorney. You can settle up your fees, etc. through another document. The only reason to use a IB's friends and family (or similar platform) is if you have many accounts and need to allocate trades among them as well as manage the fees between them.
If this is going to be a business (with you soliciting more clients) then get the right setup now because it will be difficult to switch later.
If this is going to be a business (with you soliciting more clients) then get the right setup now because it will be difficult to switch later.