I’ve never invested in real estate (except to live in), but am always intrigued by communities like FS who seem to have such a passion for it. My intrigue stems back to my earlier comments that the long term trends in appreciation in real estate are simply not very competitive versus equities, despite what Robert Kiyosaki had to say in his book, Rich Dad, Poor Dad.
Speaking of credit cards, if you don't use them to rack up debt, you can instead use them to generate income streams for you -- via their cash-back or rewards programs. Some cards offer flat-rate cash-back percentages up to about 2%. Others target certain kinds of spending or certain retailers. If you spend a lot at Amazon.com, for example, you can get a card that rewards you with 5% cash back there -- which can really add up. (It's not hard to spend $250 per month at Amazon, which is $3,000 per year -- enough to earn $150 back.)
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.