I think also a very good way to earn a nice passive income is investing in Cryptocurrency, especially in Masternode Cryptocurrencies, which provide a passive income in coins, also those carefully picked coins grow in value, so it’s a double gain! And a great coin to invest in at the moment is GINCOIN, which is the fuel for a really succesful project. Find more at GINCOIN Website: https://gincoin.io/ 😉
If you have specialized knowledge in a certain topic, you can put together an online course to teach others. For example, if you have experience in real estate investing, you can create an online course “Real Estate Investing 101”. The benefit of an online course is that once you create the course material, you can sell it to as many people as you want.