JK Rowling: ‘You will NEVER make money out of Harry Potter' How she proved everyone wrong

And yet today the Harry Potter book series is one of the best-selling of all time, with over 500 million copies sold worldwide.

While the previously broke Rowling is now believed to be worth as much as $1 billion.

A couple of years ago the Harry Potter author tweeted out the advice she wishes she’d been given when writing her first book in the series.

Rowling posted the quote: “HEY! YOU! You’re working on something and you’re thinking ‘Nobody’s gonna watch, read, listen.’ Finish it anyway.”