You can select any of the above-mentioned, based on your interest, skill, and capability to generate a second income source. However, these are just to name a few, there exist multiple ways to generate a secondary income channel. You just need to identify the right one, which suits you the best. Remember there is no shortcut to success and you need to work hard to be successful and rich in the long run!
Income inequality refers to the extent to which income is distributed in an uneven manner. It can be measured by various methods, including the Lorenz curve and the Gini coefficient. Economists generally agree that certain amounts of inequality are necessary and desirable but that excessive inequality leads to efficiency problems and social injustice.
I have only dabbled in drop-shipping before when I had an eCommerce platform 6 years ago or so. I think it is something that you could do on the side, but you would want to do in depth research on the industry you want to get into before setting up shop. It may be a little less passive up front, but over time you could take your hands off the wheel.
For a person working for a wage, their source of income is their job, or their labor (aka their time that they sell to someone). But you can own a house, and rent it out, and when your renters pay you renter every month, the source of that income check is your rental property, or your house. It would just be called rental income. If you have money in the bank in an account that pays interest, those interest payments are another source of income. We can say the source is interest payments, or we can identify the asset that is generating rent, and say your money in the bank that is generating “rent” (aka interest) is your source of income.