And that another source of income can either be a passive or an active income. I suggest that you do active income at first while trying to learn about the economy and the society that you're living at. The economy differs in every place, and the people have a different attitude about certain things at certain places. A side line is alright. You can tutor students. The pay rate is well in my country, I don't know in your place. In first world countries, the people that do not have a professional day job have to take multiple jobs in order to pay bills. That's not the case in third world countries. With just one job, you're alright here unless you have a big family and you have to feed all of them. The ones that are able to survive that type of expense are those that work abroad or those that work with a paid overtime, basically people burning out themselves to death and still live pay check to pay check.
In passive income, that's only for the people who have the time to do research about the investment that they are about to do and have the time to keep an eye on it.