I've set up some dropshipping. It's not entirely passive but it's working pretty well!
Basically, i use Ink Threadable to design T-Shirts and create mock ups. I upload these to whichever of my Depop stores is most suitable to sell the design (e.g. a t-shrit designed for teenage girls uploaded to my depop shop targeting that market). The follow bot is constantly working and the engagement is crazy. I'm getting sales irregularly but it's all pure profit which is awesome.
Once a sale rolls in, I go on to Ink Threadable and get them to print and ship the t-shirt to the buyers address as supplied to me on depop and paypal. I pay Ink Threadbare their cut and I keep the rest.
Enjoying it so far and planning on creating a boat load more shops to sell from! I want to start a homeware one selling cushion covers, another selling cool canvases with quotes on etc.
Hope that helps!