Here's a lesson I learnt the hard way:
Always Provide Value
It's one thing to ensure that you're making money on auto pilot. Trust me, no one know that better than myself.
But make sure you're providing value as well. Or else you're not going to make any money. And, if you do, it'll be short lived.
Find a mission, find a goal, find a passion. Teach others. Think about why someone would want to live in your rental property or visit your website. What value are you providing that no one else is providing? Consider that.
Answer this question first, then the money will come.
If you look for sources of passive income without a goal in mind first, you'll spin around in circles. Then your bank account will empty right out without you noticing.
Look at ways to help others. Solve a problem. Or promote a solution someone else found. That's fine too.