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.
To save time and effort, a person can group two or more of their passive activities into one larger activity, provided they form an "appropriate economic unit," according to Publication 925 - Passive Activity and At-Risk Rules. When a taxpayer does this, instead of having to provide material participation in multiple activities, they only have to provide it for the activity as a whole. In addition, if a person includes multiple activities into one group and has to dispose of one of those activities, they’ve only done away with part of a larger activity as opposed to all of a smaller one.
There’s a ton of organic traffic you can get from search engines if you do SEO properly. The days when Search Engine Optimization was about cheating Google are gone. Today, it is about making your website better for visitors. People naturally look for information online. That’s why you should learn the basics of on-page SEO, keyword research and link building to be the information source they find first. Who wouldn’t want to rank #1 for terms such as “best product” or “product review” in Google?