You can absolutely use websites like eBay and Etsy! Try listing some items and making a professional Facebook page for yourself with a link to your eBay/Etsy pages. Then share the information with friends and family and get them to spread the word to people they know. Also, make sure that you have detailed descriptions and multiple pictures with anything you list online. This will help your listing show up in keyword searches, and you are more likely to sell something if the buyer knows a lot about what they are looking at.
All of these are great ideas to earn a little more spending (or saving) money! I agree that investing in real estate can be passive, but it also depends where you invest in! If you invest in real estate in a college town (which has many pros and can give you a nice deal of money), in my opinion it doesn’t tend to be passive! College students (even the more responsible ones) tend to cause wear and tear, making your job as a landlord non-passive.
That being said, LinkConnector’s platform looks and feels outdated and is rather clumsily designed. Their dashboard also makes it difficult to find “hot” products or compare conversion rates, leaving affiliates somewhat in the dark about which products to choose. Ironically, despite their low-quality website, they offer some of the best customer service in the affiliate space.

Some commentators originally suggested that affiliate links work best in the context of the information contained within the website itself. For instance, if a website contains information pertaining to publishing a website, an affiliate link leading to a merchant's internet service provider (ISP) within that website's content would be appropriate. If a website contains information pertaining to sports, an affiliate link leading to a sporting goods website may work well within the context of the articles and information about sports. The goal, in this case, is to publish quality information on the website and provide context-oriented links to related merchant's websites.
As to copyrights, there are various ways to minimize the likelihood of theft of your work, but none are foolproof. But rest assured that if someone were to reproduce the work under their own name, they’d face legal action. It would be obvious if they were selling the work on a widespread basis. It’s amazing the information that’s making it around the web. Theft on a large scale has a way of being discovered.
Build your audience on a course community: If you’re just getting started building an audience for yourself and want to leverage communities already actively looking for content you can choose to host and sell your online course on a site like Skillshare or Udemy. These are easy, cost-effective ways to build an audience and test your niche to see if there’s demand for it.
If you have a propensity for writing and you can slay with your prose, consider writing an ebook. While the market has certainly become saturated as of late, books that help teach people about a technical topic still sell extremely well. This is a great source of passive income but does require a large amount of effort at the outset before any money is generated.