I've been hearing a lot about online courses being a lot of work but I feel like I cracked the code to making them genuinely passive. I created a few courses about niche software I use for my day job back in 2024. I barely touch them now. I update them maybe once a year if there's a big software change. Students mostly help each other in the forums and the platform handles all the payments and delivery. It's not a huge amount of money but it's consistent and truly hands off.