Percentage of AUM is a common structure for wealth management/financial advisors.
Fee only takes an up front fee, sometimes fixed, sometimes hourly.
https://www.investopedia.com/articles/investing/102014/feeon...
>Generally, though, most agree, fee-only refers to payment from fixed, flat, hourly, or percentage-based fees.
A fee based on AUM is an entirely standard way of paying a fee-only adviser.
ref. https://www.napfa.org/financial-planning/what-is-fee-only-ad...