In 2014, Jeremy Johnson found himself with time on his hands. The entrepreneur had just taken 2U, an education technology start-up that he co-founded, public. A trip to Nairobi gave him his next idea.

"Through a connection with a charity I met a group of high school girls who were getting an introduction to computer science and technology," says Mr Johnson, 33. "They were such compelling people, and I realised that the international tech community had not realised how much talent and drive was sitting right here in Africa," he says.

So he and some co-founders set up Andela, which recruits and trains young people across Africa to become software developers, then hires them out to clients including Microsoft and Google.

Andela secured $24m in its latest fundraising in June last year from the Chan Zuckerberg Initiative, a fund set up by Facebook's Mark Zuckerberg and his wife Priscilla Chan. But it does not yet make a profit.

"For now we are all about building something sustainable that is a fantastic platform for the people who are part of it," Mr Johnson says.

He does not offer a forecast for when the business will start making a profit, but says that the first of Andela's African graduates is about to start a technology business.

A study published in June by HSBC Private Bank has found that youth might partly explain Mr Johnson's long-term view on achieving profitability.

HSBC surveyed more than 4,000 entrepreneurs and found that, while the most important drivers for both younger and older entrepreneurs were the wish to be their own boss and to increase their wealth and reputation, nearly twice as many founders in their twenties wanted their businesses to have a positive impact on their communities compared to those in their fifties.

Stuart Parkinson, chief of staff at HSBC Private Bank, notes that most of the clients who tell him they are interested in funding social impact businesses tend to be millennials, a term loosely used to describe those born between 1980 and 1995.

Mr Parkinson thinks that the need to fulfil a social purpose alongside making a profit is particularly important for millennial entrepreneurs.

He points to globalisation, widespread internet access and the millennial generation's tendency to live out large parts of their lives on social media.

"In today's globally connected world it is absolutely the case that young entrepreneurs see that building social capital and having a positive social impact is as good as having financial capital," Mr Parkinson says.

"Successful entrepreneurs are in the public domain a lot more than they once were, as social media makes them far more accessible and puts them in front of a much broader audience than the financial pages [did previously]."

Investors in the social impact sector also tend to be patient, long-term investors, because they are not only focused on profit.

Nathan Elstub, chief investment officer at Nesta, a UK charity whose investments include global projects with a social benefit, says he expects the companies he funds to do well, but maybe not as quickly as more mainstream businesses.

Many of the businesses Nesta backs cater to public-sector clients. Governments tend to take longer to adopt new services than private corporations or individual consumers, he says, although revenue streams can then be longer-term and more reliable.

He adds that because Nesta backs start-ups, "they are young and growing rapidly and we encourage them to reinvest what they make back into the business". He says reinvesting, rather than looking for ways to cut costs, can help to grow the size of the business and boost a company's revenues, thereby increasing the likelihood that it will be profitmaking in the long run. Like Mr Parkinson, Mr Elstub also notes that the social impact sector does tend to attract younger entrepreneurs: "Most of the people who come in to see us are in their early 30s."

Tom Hooper, a 38-year-old entrepreneur, is a little older than that, but otherwise fits the profile. He is founder and chief executive of Third Space Learning, a British business that provides maths tutors to low-income and academically disadvantaged students.

"Like all good start-ups we are lossmaking," Mr Hooper says, adding this is because the start-up is ploughing its revenues into growing the company and that he expects to be profitable in about three years. He has his own take on the way that younger founders do business. "We are a generation that values experience over material goods," he says.

"It is good to solve a problem in a way that you can also make money out of," he adds. "But actually our generation is sick of consumption, of working just to have this or buy that. We also value how the use of our time makes us feel."