When Jamal Edwards was fifteen, careers advisers had little hope for him. Working in a fast food restaurant, they said, was the peak of his potential.

But Jamal had other ideas. Combining his two obsessions - urban music and film-making - he started creating videos of grime MCs on the streets of his native London. Jamal struck gold: by the time he was 18, his online TV channel had millions of viewers. Last month his personal fortune hit 6 million.

Most striking of all is Jamal's age: he is just 21. By giving a voice to genres that mainstream media ignored, he built a hugely successful enterprise while he was still in his teens. In an age of rocketing youth unemployment, young entrepreneursLiterally 'one who undertakes something,' the word 'entrepreneur' was first used to describe theatrical agents and managers. Nowadays it refers to businesspeople who come up with innovations in order to make money from business. like Jamal are particularly inspiring.

Among those impressed is British Prime Minister David Cameron. This week, Cameron has launched a fund offering loans to young people for startup businesses. Anybody between the ages of 18 and 24 can apply: the only requirement is a big idea and the drive to see it through.

Ideas can come from anywhere. Oliver Bridge received his inspiration in a shoe shop. By the time he was sixteen, his feet were already too large for mainstream shoe sizes. There seemed to be no easy solution - so he decided to invent one. His website, Bigger Feet, now caters to thousands of people with above-average foot sizes. By the time he finished university, Oliver owned no fewer than three startup businesses.

Dominic McVey's spark came from an even less likely source. After misspelling the word 'visa' in a Google search, he came across a foreign company called 'Viza,' which sold kick scootersScooters have been around for at least a hundred years, mostly as toys for children. But in the 1990s - partly because of Dominic McVey - they became briefly fashionable for teenagers and even businessmen.. Realising that they could be a hit among British teens, he immediately started importing them. His enterprising thinking started a craze.

Success takes sacrifices. After long days of school work, Oliver would stay up late into the night arranging orders for shoes and tweaking his website. As Jamal says, 'be prepared to limit your social life.'

But for most young entrepreneurs, the experience of achieving something from scratch is more than enough of a reward.

Jamal's best advice: 'chase your dream, not the competition, because looking at the competition will cloud your vision.'

These are inspiring stories - but the truth is, most startup businesses end in failure. It takes luck as well as determination to make a fortune in business.

But those who have had a shot at being an entrepreneur almost always say it is worth it - even if the idea is not a success. Building a business, they say, teaches you things that books and teachers never can. Even if your plan does not work out, you come out of it a stronger, smarter person.