You don't have to be Paul McCartney to rack up residuals. You might own properties that you rent out even though you're not a Realtor. Maybe a blog you started took off, and while you no longer work there, you still collect part of the profits. Or perhaps you're a serial entrepreneur who creates companies and moves on. You, too, are earning residual income.
Here's another example. If a person owns apartments that are rented out at a profit, they earn money each month without working a specific number of hours. If the owner earns $100/month net income from each apartment, the determining factor is how many apartments they own, not how many hours they work. Therefore, they may own 1 apartment and make $100 net income each month, or they could own 500 apartments and make $50,000 ($100 per apartment) each month.
Instead of buying lots of individual bonds, you can buy a bond ETF to diversify among many bonds and leave the selection to the ETF managers. Bond ETFs come in many different varieties including government, corporate, short-term, long-term, junk, municipal, international and in variations and combinations of each type. Like most investments, higher yields mean higher risk. So choose your bond ETFs based on your risk tolerance, asset type, and liquidity.
Case Schiller only tracks price appreciation of RE. RE as rental investment vehicle is measured primarily on rental yield or cap rate or some other measure. Price appreciation in that scenario is only a secondary means of growth, and arguably should be ignored as a predictor of returns when deciding on whether or not to invest in rentals. More important key performance indicators for rentals are net operating income and cash ROI. Appreciation, if it occurs, is a bonus.
Residual income is the amount of net income generated in excess of the minimum rate of return. Residual income concepts have been used in a number of contexts, including as a measurement of internal corporate performance whereby a company's management team evaluates the return generated relative to the company's minimum required return. Alternatively, in personal finance, residual income is the level of income that an individual has after the deduction of all personal debts and expenses have been paid.