The type of business you should start depends on your passion and existing skill set. If you love baking, for example, you could consider starting a home-based cake or brownie business. Love to sew? Spend your free time creating the perfect crafts, then turn around and sell them with your own Etsy store. Love dogs? Consider watching dogs out of your own home and marketing your services on a website like Rover.com.
Reality One: We live in a competitive and fast changing world. Business has become highly specialized and niched because knowledge is growing exponentially, requiring specialized skills to employ it properly. Successfully competing in many widely varying fields is contradictory to the specialization and complexity required by our current business climate.
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.