What I did:The first two years of work in NYC was brutal. I told myself there was no way I could work on Wall St for my entire career because I’d probably die from heart failure by age 40. Having an early death in my mind willed me to save 50%+ from the first year onward and devise a CD, real estate, and stock investment distribution system for my savings every year. I thought about starting this site for at least a year before I hired someone from Craigslist to give set me up and push me forward. Hiring someone to get started is totally worth it if you are a master procrastinator. You can now learn how to start your own site with my step-by-step guide to save yourself time and money. 
The one thing I learned though from all those childhood experiences though is that you never can depend on one source of income. Eventually my mom caught on and stopped giving me all those extra bags of chips and I had to figure out a new way to make money. No matter how safe something seems there’s always the chance that you could lose that income and be stuck with nothing.
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.