The kids making thousands in pocket money

Katie Mortimer is now 16 and spends up to three hours a day ordering wholesale items from China and processing packages to send out to customers. Photo / Telegraph

Enterprising children and teenagers have discovered they can boost their pocket money by thousands of pounds selling items online - without the interference of their parents.

Since the e-commerce boom in the mid-to-late Nineties, online marketplaces, such as eBay and Amazon, have given millions the wherewithal to boost their income by selling their used, unwanted or homemade goods.

But these sites were for those aged 18 or older. Now the trend is gripping a another generation of part-time traders: schoolgoing teens.

And a new wave of trading sites has leapt up to cater for them. Depop, a mobile shopping app that launched in 2012, has given children their own trading platform.

The minimum sign-up age is 14, although Katie Mortimer managed to open an account the month before her 14th birthday almost three years ago.

The phone-based trading site has more than seven million users worldwide. One in seven is under the age of 16.

By contrast, the average seller on Etsy, the online marketplace for handcrafted and vintage goods, is 38-years-old. Depop will not reveal how much its average seller makes.

But it has said that its biggest businesses take in revenues of as much as £30,000 - and that's per month.

It is three years since Katie Mortimer, now 16, turned to the internet to sell her unwanted jewellery. She hasn't looked back.

Since then she has sold £40,000 (NZ$70,000) worth of accessories, clothes, bedding and stationery bought from Chinese wholesalers and sold mainly to girls her age at prices marked up by as much as 250 per cent.

Katie believes in the time she has been selling her profits are in the order of £31,000. She was already receiving £25 a month in pocket money when she started.

This formed the seed capital of her venture. Among her first purchases were phone cases and clothes from a Chinese wholesaler.

Katie, who spends about one to three hours per day on her activities, which include processing sales, ordering stock and uploading pictures of the items on to the Depop app, said she can buy T-shirts and vests for £3 and sell them on the app for £10.50.

Phone cases cost her 50p to £1 from the supplier, which she then prices at £5 or £6.

She said: "I decide how much to sell the item for by thinking how much I would pay - and how much I think other people would pay for it. I then check that I'm making a decent profit."

She has been stung only once, when she overstocked and bought too many iPhone 4 cases. New phone models emerged soon after and she found that no one had the old phones anymore so did not want the cases.

"I think I've still got about 100 iPhone 4 cases, which I don't think I'm ever going to shift," she said.

Katie, who says she has "always loved saving", wants to have enough money to buy a car - a Fiat 500 - by the time she's old enough to drive.

She ploughs most of the profit back into the business, using it to purchase more stock.

Last August, she contributed £8,000 to the construction of a £30,000 office space in the family's garden. This is where she stores her stock and processes orders.

Sisters Bo and Eve Brearley, from London, have managed to make a full-time living selling clothes to teenage girls. When, four years ago, Bo left home to study architecture at Glasgow School of Art, Eve, who was 15 at the time, began selling her sister's clothes online.

The Brearley sisters decided to sell clothing together after Evie made £1,000 from Bo's old clothes. Photo / Telegraph

Bo, who is now 22, had no idea. She said: "I came back after the first term and saw my wardrobe had been ransacked. I was furious. But when she told me she'd give me £500, half the profits she'd made, I started thinking about it differently."

The sisters then started buying up clothes in charity shops and car-boot sales and began listing their items on Depop.

On a holiday to Italy, they discovered they could buy garments for much cheaper at "rag trade" markets - where unsold items from charity shops end up.

Once every two months, Bo flies to Italy and stays for around a week to handpick up to 80kg of clothes at these markets.

She spends €1 to €5 on each garment and says she uses "common sense" when deciding on the sale price.

"When items sell in about 30 seconds, we know to increase the price the next time; if we can't sell something we know people think it costs too much."

While Bo and her sister work hard selling between 400 and 500 garments a week, spending hours photographing each item, which Eve models, packing and posting the items and responding to customers, she said online selling is an "easy way for young people to make a bit of extra money".

She said: "If your parents bought you the clothes, selling them means a straight profit."

Parents generally applaud children's entrepreneaurialism, but other experts express some doubts.

Jane Evans, a childhood anxiety and parenting expert, warned of the additional stress that could be experienced by children who allow themselves to be "dragged into the world of money" via online selling.

She said: "It's stressful being a teen, full stop. Then imagine having to work out the latest trends in a competitive environment, while trying to stand out as a brand. Some children are at risk of being caught up in the frenzy.

"We know that children are prone to addictive behaviour, especially where technology is concerned."

Evans said online marketplaces might appear to be connecting users - but they could also cause divisions between children and their friends and family in real life.

As well as trading on the internet, children as young as 13 increasingly top up pocket money through survey sites, where they answer lifestyle questions.

While sites such as Depop allow young teens to sign up, they generally have to have a PayPal account - for which you need to be 18 - or permission to use another adult's account.