Email marketing is one of the best ways to develop passive income. If you use an autoresponder company (and you definitely should), you can write and store emails in your account that automatically get sent out to your list subscribers. These emails can contain links that sell products you believe in—either your own products or products you’re promoting as an affiliate.
You could choose to store enough content to last a year or more, if you wanted to. Write 100 emails over time, add links to them, and load them up into your autoresponder account. Set them to deliver every few days or a couple times a week or whatever works for you.
How is this passive? It’s passive because these emails will go out to new subscribers at the preset intervals you’ve determined ahead of time. Ideally, you’ll design a list-building funnel that will work for you day and night. So, someone who joins your list today will get your email sequence in order—they’ll see the emails where you teach things and emails where you sell things. They’ll buy from you.