Leveraging the internet to create, connect, and sell is something every creative person should attempt to do. The only risk is lost time and a wounded ego. You can start a site like mine for as little as $2.95 a month with Bluehost and go from there. They give you a free domain name for a year. Forget all the add-ons. Not a day goes by that I’m not grateful for my site.
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.