An analysis of the firm's position in its industry and the structure of the industry will be necessary to justify one of these assumptions. The third scenario is the most realistic if we assume that over time, industry competition reduces economic profits to the point at which firms begin to leave the industry and ROE stabilizes at a long-run normal level. The strength of the persistence factor will depend partly on the sustainability of the firm's competitive advantage and the structure of the industry. The more sustainable the competitive advantage and the better the industry prospects, the higher the persistence factor.
The right niche -- If no one is searching for information in a niche, you won't get traffic, and you won't be able to convert that traffic into blogging income. That said, you could take a traditionally low-income or low-interest niche and twist it into something more attractive to readers, such as by combining two niches, broadening it, or even narrowing it.
Investing in the stock market is a classic form of passive income. As you might know, with stock markets, there is some risk involved. But then again, virtually all residual income methods involve a level of risk, and you won’t find any idea that’s risk-free. In fact, stock marketing can be one of the least risky ways to earn money, if you invest smartly. The basic rules apply: Create a diverse portfolio, start with around $1,000, learn about the stock market, and create a back-up fund.

All the little bits of money you earn through those channels can make up quite a nice sum after a year or so. Remember how I said that starting a passive income business either a lot of time or some money, or a bit of both? Well, mobile apps offer the best of both worlds. With a little time and a little money you can have an app developed and on the App Store in literally a week.
People love talking about passive income online. But, everyone seems to have a different view on what’s passive. For me as a blogger, it means doing the work once and continuing to earn money on that work for months or years down the road with minimal upkeep. Sorry, folks. Passive income doesn’t mean getting paid for doing nothing ever. You've got to put in some effort.
Peer-to-Peer Lending: Earn up to 10% in returns by lending individuals, organizations and small companies who don't qualify for traditional financing through peer-to-peer lending platforms like Lending Club. You can lend $100, $1,000, or more to borrowers who meet lending platform financial standards. Like a bank, you'll earn interest on the loan - often at higher returns than banks usually get.
As a private lender, you can lend to anyone in your social circle. For example, many home rehabbers need access to a source of capital they can tap into very quickly in order to fund the initial purchase of their properties. You can partner with a rehabber who uses your capital for a short-term in exchange for an interest rate that is mutually agreed upon.

It might all seem pedantic but I think the words we use to describe things are important. And calling a business passive when it really isn’t can set people up for disappointment and even failure. It’s not a fair description of the work involved. Sure, you might be able to lounge on a beach as money rolls in but only after you’ve put in many hours of work first and only with the knowledge that you’ll have to sit back down at the computer again at some point to invest further in your business.
"Residual disability" is generally defined as the inability to perform one or more duties of your occupation, or the inability to perform these duties as often as before, coupled with the loss of a significant percentage of your pre-disability income. While "partial disability" is similar to residual disability, the ways in which benefits are calculated for these two types of coverage differ.

This book is a definite must read, and in the top 5 out of this list.  My favorite use for this book is to help people decide what business model to pursue – for a start anyway.  ie info product v membership site v affiliate marketing.  Since Joel compares them all and shows you the major challenges for each (along with how-to guides), the task becomes a lot easier.