I keep myself within my skill and talent set, yet apply them to long-term projects.
Within 30 days, an eco-educational text will be coming out. A nice 100-pager. A three-year project has resulted in a 465-page, 126,000-word Novel. That one is scheduled for release in January 2021.
These are "side jobs" that are start-finish, can provide residual income, and are a pleasant integration into my business writing day.
Net. Pick a long-term project that will make you money. Let your "side hustle" be strategic in nature, enjoy the ride, and make money with strategic time frames involved. Risk more, make more and let the daily work take care of the rent and food.