If you have specific writing/journalism skills or are adept in various IT/software domains, freelancing may prove to be a lucrative source of secondary income. Increasingly, companies are implementing a content marketing strategy and turning to outside sources for specific assignments, and if you can prove your worth there will be more work available. Even simple skills like data entry may be to your liking, provide you can offer at least 5-10 hours weekly.
All you need is a computer with an Internet connection and the desire to build a respectable clientele. Chances are that these opportunities will allow you to gain valuable experience and skills that will prove valuable in your existing business and professional career.
If you’re already writing ebooks in a particular niche market (see above) then why not make your services available for other companies; as you already have the expertise to take on the niche writing assignments.
Though it’s not really a passive income stream, doing freelance work is one of the fastest ways to generate income.