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.
Be proactive. Remember Murphy's Law: "Whatever can go wrong will go wrong." Make plans, complete with as many calculations as possible, then anticipate everything that can go wrong. Then make contingency or backup plans for each scenario. Don't leave anything to luck. If you're writing a business plan, for example, do your best to estimate when you'll break even, then multiply that time frame by three to get a more realistic date; and after you've identified all the costs, add 20% to that for costs that will come up that you didn't anticipate. Your best defense against Murphy's law is to assume the worst, and brace yourself. An appropriate amount of insurance may be something worth considering. Don't forget the advice of Louis Pasteur, a French chemist who made several incredible breakthroughs in the causes and prevention of disease: "Luck favors the prepared mind."
To get started with side hustling, let your friends and family know about your desire for more work. Your network is your net worth in this regard, and can play a powerful role in helping you secure more gigs. It can be surprising how much your network can propel things further simply by asking. But you have to take the first step and ask! Send out personalized emails and post on social media.