Plenty of online marketplaces exist to sell web design, writing, and other common skills. But one marketplace in particular, People Per Hour, allows you to sell a well defined service. For instance, if you studied interior design, you could set a fixed price to design someone’s studio apartment. The marketplace is great and allows you to be more creative with what you can offer based on your actual background.
Many people talk about passive income and create the impression that you never have to do anything to keep that income going. The truth is that you will normally have to keep your eye on things if you want it to run smoothly. For example Richard Branson doesn’t run any of the 400+ companies he started but he goes over the numbers each day to make sure they’re performing well and calls the CEO if there are any problems.