Earning sources include books, courses, merchandise, coaching, freelancing, speaking, training, selling advertising, and affiliate marketing. For example, a virtual assistant can create tangible or digital products, such as books, courses, and videos that teach others how to be a virtual assistant in the “products” spoke. For services, she can offer additional services, coaching or speaking (i.e., How a Virtual Assistant Can Save Businesses Time and Money). Under other, she can expand her business by bringing on contract virtual assistants and become a manager of a VA company. Not all businesses will be able to come up with ideas for each spoke, but every business should be able to develop extra income streams from their home business idea.
Ebooks are one of my favorite sources of passive income. Now, you can do this the simple way and just publish it on Amazon's KDP. Or, you can go all out and build yourself a book funnel. Book funnels are powerful, but they won't be fully passive. For example, if you do a free-plus-shipping offer for your ebook (converting it into a physical book), you'll need to create some one-time offers (i.e. extra training) and up-sells (i.e. an audiobook). But, a book funnel can be very powerful.
Another way to generate passive income is to invest and be a silent partner in a business. This is very risky, but with risk comes the potential for high returns. For example, several years ago both Lyft and Uber were looking for private investors to invest in their companies. Today, they are worth billions - but you as an investor would only reap that benefit if they go public via an IPO, or get acquired. So, it's risky.
If you can max out your 401k or max out your IRA and then save an additional 20%+ of your after-tax, after-retirement contribution, good things really start to happen. If one is looking for earlier financial independence, such as retiring in their 40s or early 50s, it may be a good idea to skew towards more after-tax savings and investments given one has to wait until 59.5 to withdraw from their 401k or IRA penalty-free.
That $200,000 a year might sound like a lot to you, but the median home price in San Francisco is roughly $1.6 million or almost eight times our annual passive income. For a family of three in 2018, the Department of Housing and Urban Development declared that income of $105,700 or below was "low income." Therefore, I consider us firmly in the middle class.
Most of us think of investment income as just the cash flow we get from bank interest, bonds, share dividends and property rents, some of which comes via a super pension.  But a more complete view is to also consider how growing the value of your investments can add to your spending potential.  This total return approach generates income from both income and growth to optimise spending from your portfolio across all market cycles, aligning cheap and expensive investments to your goals.