The key idea is: not to sell your time.
In market economies most people sell their time:
In all cases, there is a limit to the hourly rate you can charge: from minimum wages, to the rate of top-notch lawyers or surgeons.
At best, you can become well-off, but you cannot really get rich.
For that, you need to disconnect your revenues from the time you put into generating them.
Among the traditional ways to generate revenues disconnected from time are:
If you received, via inheritance or otherwise, a large capital, you can put it to work: for instance in real-estate (buying flats to rent, as said), or buying safe long term bonds producing coupons.
In the stockmarket, aside from acquiring a revenue generating asset (more or less safe, more or less like a bond), you can gamble on the variations of value of securities:
But you take risk. Selling short for instance is highly risky.
When playing the stockmarket, you can either use the Modern Financial Theory. But this, once in a while, offers a free big laugh, like when two Nobel prizes advising the fund LTCM lead it to a huge bankruptcy which needed of $4 billion clean-up from other banks. They thought that you can eliminate risk using MFT. But that was true only inside their models.
Or you can, like Warren Buffett, turn your back to MFT, and buy when the market is depressed and sell when it is buoyant. He often explained how he does. You need to be very patient. Besides, Buffett doesn't really create value, but rather surfs intelligently on markets.
When, with a large capital, you buy a healthy firm, what you acquire, in truth, is a stream of future revenues. Unless the firm is a key to your other activities (like Skype was to eBay) you don't create value. If the seller is smart, anyway you pay a price close to the value to you. You still take risk. And you still need to spend time taking care of your investment.
Some people manage to consistently win money with horse race betting. They understand finely the mechanisms of odds and bets and know which bets have a positive net expectation. They are discreet about their techniques. You need however to spend a lot of time keeping informed on horses and riders.
The economy of the XXIst century, and more specifically Internet, allows us to build assets which:
A website is like a shop which immediately can tap a market comprising hundreds of millions of clients.
If the website sells online things which can be reproduced at no cost (like with a cookie cutter), and sold at very little or no cost, the potential revenues are boundless.
An alternative way is to make them free, and rent space on the site pages to advertisers. (This is the business model, for example, of free daily newspapers distributed in the subway every morning.)
Of course, if the attractiveness of your site depends on news which must be refreshed daily, you are still selling your time.
Google is actually the world biggest advertising network, managing relationships between advertisers and publishers, and the cash flows between them (taking a margin in the middle).
In 2009 Google year end documents were (in billion of dollars) as follows:
97% of Google revenues come from ads on their sites. Half of the complement comes from ads on partners sites, and the other half from everything else.
Of course building a website which attracts visitors and has traffic will take a lot of time, thinking and effort. But then it will generate revenues disconnected from the time put in it.