As much as possible - treat it like a full-time job if you want it to replace your full-time job. That way, you'll grow so fast that you can start earning more freedom as early as the second month.
Otherwise, it's perfectly fine to work 5 hours a week. You'll grow slower, but you'll be earning your first $1,000 online in a short time. Almost everyone starts this business as a side hustle, devoting a couple of hours to it in the evening or several hours on the weekend.
What you put into the business is what will come back to you. The more money you invest, the more time you invest, and the more you will earn. More investment = more results.