Writing roles can come in any industry. Businesses need writers to create sales and marketing copy as they create and update online stores. They need writers who can provide clean, clear instructions for a digital manual (which falls under “technical writing”) or just good, valuable content. Full-time writing jobs in advertising, marketing, branded content (B2B and B2C) and sales are definitely available, because businesses are always changing and updating their on their websites and other media where branding and messaging takes place.
With apps being constantly developed, competent app developers are in high demand. Again, if you have the experience or skills to create successful apps then this could be something you could end up working on as a full-time freelancer. Check out adverts for developers on Toptal, a higher paying jobs site for experienced freelancers wanting to make money online.
Depending on your skill set, you could easily make a few hundred dollars or even a few extra thousand per month. And if you have some money to invest, you could easily launch into a variety of day trading activities. Those present some risks of your original capital. But if you know what you're doing and you work to hedge your bets by placing stops and limits, you could create sizable upside with lower-than-usual risks.