In terms of whether transactions are liable to tax, the important distinction is that when you bought what you intend selling, you did not buy it with the intention to sell it on at a profit. For example, if you repeatedly buy and sell vintage dresses on eBay at a profit, then these transactions will be considered trades and you ought to include your profits in taxable income.
Now, all that said, if capital (savings) grows faster than the growth of the economy, those with savings will see their wealth grow at a faster rate than those who rely on the growth of their income. While this is not an extension of Piketty's argument (you can't take an idea that applies to a population and a whole economy and boil it down to the individual like this), it's not an unreasonable conclusion to take and apply to your own life. (Piketty does talk about this on an individual level, but says it's more impactful for billionaires vs. millionaires – though we have limited data into individuals)

I think more and more people are recognizing the advantages of having multiple sources of income, thanks to the Great Recession. It was a real wake-up call to many good workers who lost jobs not because of poor performance but due to restructuring and cost-savings. They never considered themselves to be vulnerable and they were. We do have multiple streams of income and a fully-funded emergency fund, which has helped my family weather the ups and down life has brought us, including job loss.
With $200,000 a year in passive income, I would have enough income to provide for a family of up to four in San Francisco, given we bought a modest home in 2014. Now that we have a son, I'm happy to say that $200,000 indeed does seem like enough, especially if we can win the public-school lottery to avoid paying $20,000 to $50,000 a year in private-school tuition.
I run several online businesses now (all it takes to start one is a domain, hosting, and maybe incorporation). There are two notable ones. The first is meal plan membership site called $5 Meal Plan that I co-founded with Erin Chase of $5 Dinners. The second is the umbrella of blogs I run, including this one and Scotch Addict. They pay me ordinary income as well as qualified distributions since I'm a partner.
In federal legislation, the key planks for the right to a useful and remunerative job included the National Labor Relations Act of 1935 and the Fair Labor Standards Act of 1938. After the war was the Employment Act of 1946, which created an objective for the government to eliminate unemployment; and the Civil Rights Act of 1964, which prohibited unjustified discrimination in the workplace and in access to public and private services. They remained some of the key elements of labor law. The rights to food and fair agricultural wages was assured by numerous Acts on agriculture in the United States and by the Food Stamp Act of 1964. The right to freedom from unfair competition was primarily seen to be achievable through the Federal Trade Commission and the Department of Justice's enforcement of both the Sherman Act of 1890 and the Clayton Act of 1914, with some minor later amendments. The most significant program of change occurred through Lyndon B. Johnson's Great Society. The right to housing was developed through a policy of subsidies and government building under the Housing and Urban Development Act of 1965. The right to health care was partly improved by the Social Security Act of 1965 and more recently the Patient Protection and Affordable Care Act of 2010. The Social Security Act of 1935 had laid the groundwork for protection from fear of old age, sickness, accident and unemployment. The right to a decent education was shaped heavily by Supreme Court jurisprudence and the administration of education was left to the states, particularly with Brown v. Board of Education. A legislative framework developed through the Elementary and Secondary Education Act of 1965 and in higher education a measure of improvement began with federal assistance and regulation in the Higher Education Act of 1965.
I remember seeing a number of my co-workers get laid off in 2008 and many of them had only worked for the one company. They had mortgages to pay, colleges to pay and families to support and they were scared out of their minds for what they would do next. After watching that happen, I vowed that I wouldn’t suffer the same fate. It’s one of the main reasons I started my own company. I tell people now that instead of one boss (i.e. one company), I have hundreds of bosses and it makes me feel more secure about my longterm prospects.
That's odd, because lot of these questions are actually pretty easy to answer. The IRS is good about publishing the data. Given that – and given the recent interest in personal income inequality, I decided to write a little bit about the different kinds of income people report on their tax returns. A longer paper – Sources of Personal Income – is here, but for a brief overview, you might want to check out the top ten sources of income:
How To Engineer Your Layoff – In 2012, it took me four months of absolute focus and two years of data to publish my first e-book about helping people negotiate a severance. The book went through over 30 revisions by four people. Then I updated the book for 2018 with 50 more pages (150 pages total) using more successful case studies and highlighting more strategies for those who want to break free with money in their pocket.
I cut back on medicolegal work to free up time and reduce stress. I spend most of my time on medical directorship work and clinical practice. Free time is spent on exercising, travel, time with family, and blogging. I spend virtually no time on the other income streams at this point. Getting the plate spinning can be tough but then the momentum keeps them turning.
But two months later, with the economy slowing down after the financial crisis, his firm began laying people off, and Flynn was informed that after his current projects were finished, he also would be out of a job. At the same time, he couldn’t help but notice that in the LEED exam forums he had frequented, people were referring to him as an expert and directing questions his way. He began to think he might capitalize on that.
Build an investment portfolio that pays out dividends (Stocks / Bonds / Mutual Funds). Dividends are payouts that companies give to their investors as a portion of their earnings. They’re often paid out quarterly. If you’ve already got an investment portfolio, it’s time to take a good look at which stocks, bonds, or mutual funds you own. You’ll see consistent returns from the ones that pay dividends. This is a fantastic way to earn passive income. Invest once and watch the returns pile up.

Stocks (shares) paying dividends are typically a reliable source of income but they have higher risk of capital losses than cash and bonds. So, it’s wise not to chase yield indiscriminately.  The 10 highest yielding stocks on the ASX 200 (the 200 largest companies in Australia) are shown in the table below.  But their share price performance on average over the last year has been underwhelming, as shown in the far right column:
What I Do: I’ve set up multiple investment accounts outside my main operations bank that deals with working capital e.g checking, paying bills. By transferring my money to a couple brokerage accounts and two other banks as soon as it hits my main bank I no longer have temptation to spend on frivolous things. As a result, I can wake up 10 years later and reap the rewards of compounding. My 401(k) is the best example where constant contributions over 18 years has grown to over $500,000 without any savings pain given it just became a part of life. Real estate is also a fantastic asset class for the long term. It’s fantastic to enjoy your home, pay down your mortgage each month, and end up with a paid off asset that has likely appreciated during your time of ownership. 
Investing in coins and collectibles: Buffalo nickels and Spiderman comic books are good examples of coins and collectibles that can rise in value, and thus offer opportunity for passive income investors. You'll need to get up to speed on the value of any coin or collectible under consideration, but once you do so, you're on the way to price appreciation on a commodity you'll be paying a lower price to buy, and will garner a higher price when you sell.
I wouldn't think of a high yield savings account as a source of passive income but your savings should be getting something (less like Seinfeld syndication residuals and more like a commercial jingle residuals!). It won't make you rich but it's nice if your baseline, risk-free rate of return on cash is 1% or more. The best high yield savings accounts (or money market accounts) offer higher interest rate and there is absolutely no risk. CIT Bank currently leads the pack with the highest interest rate.
Andrew Rafal, Founder and President of Bayntree Wealth Advisors in Arizona, recently told me about his push to get clients to diversify their income streams. The Great Recession feels like an eternity ago now that the economy is looking up, he says. The job market is strong and consumer confidence is through the roof. As a result, it’s possible people are getting a little too comfortable.