Now that we've found how to compute residual income, we must now use this information to formulate a true value estimate for a firm. Like other absolute valuation approaches, the concept of discounting future earnings is put to use in residual income modeling as well. The intrinsic, or fair value, of a company's stock using the residual income approach, can be broken down into its book value and the present values of its expected future residual incomes, as illustrated in the formula below.
Investing in a business: Another good way to generate passive income is to invest in a business --even a small one -- in return for a percentage of the profits - just like Shark Tank, only smaller. Lending $10,000 to a local business that, for example, is working on a mobile app for Apple phones could lead to a passive income-generated share of the profits when that mobile app starts selling like hot cakes.
As we know, Amazon has invested (and still is investing) heavily in the navigation / recommendation functionality of their shopping platform: there is not only Advanced search and faceted filtering, but also features like “Frequently bought together”, “Customers Who Bought This Item Also Bought”, “What Other Items Do Customers Buy After Viewing This Item?”, categories/tags, new releases, best sellers, various public wishlists, registries…
The second big takeaway for me, was to pick a niche you know, you find interesting AND where there is demand for your product – ie willingness to buy/pay.  A lot of people only remember the first part of this 2-part formula, and end up creating a blog on knitwear for kittens.  But it’s the overlap of passion and profit that Ferriss stressed so much.