The author of the following quote is either ignorant of the facts or guilty of willful evasion – I suspect the second but will answer as if the author is simply unaware of all the errors in his quote.
“You think J.K.Rowling made and stocked and sold the books she wrote, you think Gates wrote the software he got rich from? Tens of thousands were employed making and selling the products these billionaires are famous for, working extreme hours or for deflated wages while the value total of their work was given mostly to a figurehead in amounts where they not only could never enjoy it all personally, but to the point where the wealth they're sitting on could be used to solve problems of health or poverty on national or even global scale.
Suppose you own a piece of property for which you paid 300 thousand. You decide to invest another 500 thousand and build a house on your lot. You did your research and you purchased a lot that’s in a location that’s in demand. Further, you know what people want and you have excellent taste. You sell the house for 1.4 million – your profit is 600 thousand.
Did you make your money on the backs of all the tradesmen that worked on your house? Did you force the electricians, the plumbers, the framers to work for you? Did you force them to work “extreme hours for deflated wages.” Or did they work for you of their own free will because the money you paid them was worth more to them than their time? Everyone that worked for you, everyone that worked for J.K.Rowling, every one that worked for Bill Gates worked of their own free will. The “tens of thousands” all made a gain – they all were win-win relationships. That’s how the free market works; that’s how capitalism works.
Billionaires are not “sitting on their wealth.” Even if they just put it in the bank, the money gets invested which creates jobs and the poor need jobs far more than they need a handout.
Finally, what does it take to become a billionaire? The answer should be obvious. One must offer something that not just a few people want, but something that millions or tens of millions want and see as a value. J.K.Rowling gave the world stories and movies that people liked and loved. Bill Gates improved the life of virtually every human being on the planet. Both should be praised not criticized for being billionaires. Being a billionaire should be a badge of honour.