If you are the author or original creator of a commercial work, the content you create based on that work does not qualify as fan art.
For example, illustrations featuring characters from a manga series you have commercially published are not considered fan art.
However, the ability to monetize such content depends on the agreements you have with any publishers or rights holders involved. Content providers need to check these details directly with the respective parties.
Please note that we are unable to offer guidance on third-party policies.