Domain names cannot be replicated. If one is taken, the only recourse would be to approach the owner to discuss a sale. While there are other variations you could choose, sometimes owning a certain domain (especially if it is attached to your business) can be worth the premium. Often, people will scout out domain names that are still available, buy them, and then sit on them in order to sell them down the road. Depending on who may want the domain down the road, you could sell it for a large markup.
This is the standard affiliate marketing structure. In this program, the merchant pays the affiliate a percentage of the sale price of the product after the consumer purchases the product as a result of the affiliate’s marketing strategies. In other words, the affiliate must actually get the investor to invest in the product before they are compensated.
An affiliate marketing program is a lot of work, and in most situations there's a lot of competition so you're not going to be bringing in money immediately. Business owners and entrepreneurs suppose that all you need do is setup a site and choose an affiliate to associate with and then just let it run its course. But according to Three Ladders Marketing, only 0.6% of affiliate marketers surveyed have been in the game since 2013. That means that affiliate marketing takes time and effort to build and make money.
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.