I can get it for you wholesale . . .: You're delighted because you bought a quartz watch for pounds 1 at a car-boot sale? It cost 35p. John Windsor looks at the lucrative world of market trading

As car-boot sales and weekend markets proliferate, do you ever wonder where the increasingly professional traders get their goods from? How can they sell shirts for half the shop price and still earn enough to drive Range Rovers? The answer lies in the back pages of trade magazines and newspapers.

Once these publications were the fiercely guarded preserve of professional traders. Only they could buy goods at wholesale prices in wholesale quantities. But the recession and the metamorphosis in shopping patterns has changed all that.

Many hard-pressed high-street clothing and household wholesalers in London's Whitechapel and Brick Lane have abandoned the traditional pounds 100 'minimum spend' which kept out retail customers. This takes the pressure off traders to hold large quantities of stock, while also opening the doors to any buyer with pounds 50 to spend.

Some wholesalers are brazenly cashing in on their new-found retail market. Clothing wholesalers in Narborough Road, Leicester, switch from wholesale to retail on Saturdays, raising prices by 25 per cent. It is a topsy-turvey world. As Glenn Mabey, publisher of the Trader, says: 'Everyone is trying to make money without offending their core business. It is a juggling act.'

Meanwhile, professional traders have invaded the amateurs' car-boot sales, once the preserve of those basking in a villagey bring-and-buy atmosphere. The lure for professionals is low rent (a fiver a day instead of pounds 20- pounds 25 for a market pitch), lack of local-authority traders' registration and, for some, the ease of palming off stolen goods.

What was to have been the country's first all-night car-boot sale - banned one Saturday last month by a court injunction granted to Tower Hamlets council - was for professional 'booters' who, having traded in markets all week, needed to spend the daylight hours of Saturday buying stock.

Trade publications now carry advertisements for packages of goods priced pounds 30 to pounds 100, suitable not only for market traders but for amateur booters and 'planners' - organisers of Tupperware-style home sales.

Sale-or-return is common. Clothing is still the biggest market, but the latest fads include aromatherapy oils and natural cosmetics.

Every month, the Trader (circulation 30,000) publishes up to 300 pages of wholesale stock advertisements. One Essex wholesaler (adhering to the 'trade only, minimum pounds 100' tradition) offers loo rolls at 36 for pounds 4 - giving a pounds 5 profit at the market-stall price of four for pounds 1. Black bin-bags - pounds 21.25 per 1,000 - sell for pounds 50 if packaged at 10 for 50p. Fancy earrings, selling in markets for pounds 1 each, cost pounds 18.75 for 100 or pounds 124.99 for 1,000 through a trade press advertisement.

If you thought your disposable lighter or tube of superglue was cheap at 50p, Trader advertisers offer lighters for 10p each (with unspecified 'bulk discounts') and tubes of superglue at 22p each. Sunglasses can be had for pounds 299 per gross wholesale, complete with revolving display unit and tags proclaiming prices such as pounds 15.99 and pounds 18.99. As for quartz watches: you think pounds 1 is cheap? Cheapest wholesale price is 35p.

Amateur booters itching to invade the professionals' ground in real markets now find 'getting on' (getting a pitch) easier because the number of markets has risen by 20 per cent in five years, to about 1,200. Private operators have led the expansion. They now control 30 per cent of markets, some formerly under local authority control.

Successful traders are coining it. The Trader found that 8 per cent of the market traders it surveyed had an annual turnover of pounds 100,000 or more and half of them turned over more than pounds 20,000. No wonder high-street retail sales are languishing.

The market traders' traditional read is the original trade newspaper, World's Fair (circulation 27,000, published with Market Trader and CoinSlot). The weekly free papers Marketeer and Discount Trader and the monthly Wholesaler have circulations of 31,000 and 6,000. The biggest growth area in market-trade publishing is guides to the country's 1,000 factory shops (see below), another recession-inspired wholesale market serving both traders and retail buyers, which is dominating retailing in the United States.

Many suppliers agree not to sell store-commissioned designs elsewhere for six months. But there is nothing to stop them calling them 'seconds' - without the big-name label. Other suppliers are simply exploiting 'direct sales' as a lucrative new market.

David Glasby, secretary of the Association of Private Market Operators, buys the clothes he wears - at a fraction of high-street store prices - from the very factories that supply the stores. Among his bargains, all bought in small numbers: shirts by Coats Viyella at pounds 1.99 each and a pounds 9.50 cotton dressing gown which in the high street would cost pounds 29.50.

Industrial and commercial auctions also offer cheap gear. At a liquidation sale in Queensbury, West Yorkshire, Mr Glasby bid pounds 170 for enough magazines and books to fill a double garage - including Playboy and body-building mags - which later raised pounds 2,000 retail. Only half a dozen people attended the sale.

Magazines: The Trader: pounds 1.40, subscriptions (0202 445000); World's Fair, Market Trader and Shopkeeper, CoinSlot, 60p weekly for all three, subscriptions (061-624 3687); Marketeer and Discount Trader, free, pounds 16.50 annual postage; The Wholesaler, free, pounds 6 annual postage (0604 710722); Government Auction News, monthly, pounds 39.50 a year; The Wholesale and Direct Buyer's Guide, pounds 12.95 inc p&p (071-734 8291/4). Auction News, weekly, pounds 75 a year (0332 551300).

Factory shops: The Factory Shop Guide, 10 editions: British regions pounds 3.95 or pounds 4.50 plus p&p (071-622 3722). The Ultimate Bargain Hunters' Handbook, pounds 12.95 - pounds 11 inc p&p to Independent readers (081-429 3030).