I’m not a fan of the term “passive income”. Usually I say, “semi-passive” meaning you have to do a little bit of work. But writing and publishing eBooks is about as passive as it gets. Once the book is done there really isn’t much to do besides wait for the money to come in. That definitely makes it a huge benefit to making money online if you don’t want to deal with marketing or customers.
A lot depends on the extent to which you promote your audiobook and how visible it is on platforms such as Audible and iTunes. If you’re lucky, a successful audiobook can generate a five-figure annual income stream. More obscure titles might earn just a few hundred bucks per year.

Browser extensions, like Honey, easily help you find coupons and automatically apply them to your purchases so you can always get the best deals. You also get a great cash-back in the meantime!
So… if you have some time in hand (while you are doing other things on the list to get free money fast), you can start pitching editors of different publishers that pay contributors.