Let's talk about hosting websites like Redbubble, Etsy,

These aren't "hosting" sites - they are Print-On-Demand sites. I don't know why you included Etsy in this group, as it's a different thing entirely.

Used to pull in around $800/mo collectively from multiple PoD sites, doing basically nothing and making on-site sales. I've seen these sales have dropped every year, as the search algorithms change and the way artists are featured changes. I'm now pulling in around $350/mo if I'm lucky. Redbubble used to be the most noobie-friendly with how they featured new artists, but I don't think that happens very often.

The two ways to make money on these sites are to
1. Play the patience game and wait years until your work creeps its way onto the "popular" pages.
2. Develop a large and engaged audience for your work, and point them to your sites

Both ways are incredibly difficult. If you're going to go with #2, I recommend using a Threadless Artist Shop - they have the highest margins by far.