As for me, I started focusing on passive income last year, but have owned rentals for 5 years. $25k now outside retirement accounts in mostly real estate. Looking to invest another $500k cash into real estate to get about $65k, and then 1031 under performers next year to hopefully boost that a bit higher. Heavy in real estate, but feels lower risk than the stock market to me if you have cashflowing properties. Real estate is inflation adjusted, and built in cashflow raise when the loan pays off.
Portfolio income can come from multiple sources – interest/bond coupons, stock dividends, financial strategies including derivatives and capital growth.  Each offers some cash flow and some also offer potential capital gain with some risk from liquidity and volatile prices.  In this low-yield environment, many investors rely too heavily on cash flows and to pursue this are venturing further into riskier areas than they’d normally consider.