How do you do this?  Well, try to get the highest paying job you can!  Ask for a raise!  Utilize services, such as, to see how your salary competes with others in your same job.  Some companies really force employees to leave to get a raise, and then come back for another raise.   This industry jumping promotional strategy is very common and could work.
Multiple streams of Income covers this strategy. I highly recomend you read it if for that reason alone. Beats the typcial buy and hold (or is that buy and hope), dollar cost averaging and other so called sensible stategies which don't work unless you have a 20-30 year time horizon. Ask anyone who saw their investments plumet during the Jimmy Carter years back in the 70's how long they had to wait to get their investments back up to break even level. Want to take a guess? Would you believe 15 years? That is close.
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.