Most people fall in the 5–15 hours per week range once things are set up. In the beginning you’ll probably spend more because you’re testing products, fixing listings, and figuring out what actually works. but after that, it’s mostly checking orders, replying to a few messages, tweaking ads, and doing small optimizations.
Some weeks you barely touch it, other weeks you might grind a bit more, but on average it’s nowhere near full-time unless you’re trying to scale aggressively.