Answer:
Depends on the age and region.
Explanation:
If you are at least 16, working is the best answer. Everything else is snake oil and guess work. Paychecks are guaranteed in most countries and if the paycheck isn't, you can always quit if they jip you out of one.
That said, if you are beneath 16 I would look into online means. Surveys are scams but if you can do mturk through Amazon you can at least be scammed by a major corporation. I would suggest looking into Fiverr if you have skills worth paying for. There is also Etsy or even art websites if your talents stray into the creative realm. There are translation apps and opportunities if you can speak multiple languages.
Otherwise, dog walking, lawn maintenance. and baby sitting are all common income streams for youth. You can also give lessons in person if you are academically inclined or know an instrument well.
If all else fails, build a skill! Learning coding is easier than ever. You can learn a new language through hundreds of apps. Investing in yourself is a solid way to make money tomorrow.
