The study about an millionaire having 7 sources of income is often misunderstood and misquoted. I believe this is the original report : https://www.irs.gov/pub/irs-soi/14rpoverthetopbournerosenmer... and then multiple streams that people often quote are not multiple streams, but multiple forms, like investment income, rental income, royalties, earned income etc.

The study is actually quite insightful if you read it for what it is and not what you want it to be.

I have also found this video to be quite insightful : https://www.youtube.com/watch?v=NF5H7ch2Ngg