You can create a passive income online by setting up a blog on a high paying niche or something you're passionate about.
It will require lots of work in the beginning and you likely won't earn much if anything at all in the beginning but years down the road you should see the cash start rolling in without you having to do much work.
You still have to update your blog and keep it fresh but you won't have to work as hard at it as you did in the beginning and you could earn money from your blog while you sleep.