It was not long after Glenn Kelman launched Redfin.com, a new service for US house hunters, that the first hate mail arrived. “People sent us e-mails saying someone would break our knee caps so we’d better watch it,” he says. As an online real estate brokerage with no field agents and reduced transaction fees, his service has “engendered resistance on a new scale” from traditional industry players, he told a Congressional committee over the summer. “Many of our customers have been told they can’t see a [house] or make an offer if they’re represented by us.”

It’s not hard to see why Kelman, a 35-year-old entrepreneur backed by Microsoft pioneer Paul Allen, is seen as a threat. In an age when millions of consumers now book flights, buy groceries and even conduct love affairs online, his company and others like it are out to prove that the internet can make house purchases – the single biggest transaction most people make – more transparent, more efficient and less expensive, too.

“A brokerage that doesn’t employ agents is a radically new service at a radically new price,” Kelman says.

“We think people can save thousands of pounds,” says Helen Probert, the 28-year-old founder of Cutthemiddleman.co.uk, one of about 100 UK-based self-sell websites. “Estate agents are going to be a thing of the past.”

“In five to 10 years estate agents will be entirely redundant,” agrees 30-year old Andrew Binstock, who runs Auctionyourproperty.com from his house in north London. He calls up an array of e-mails from clients on his computer screen. “I hate estate agents,” begins one message.

For several years, the internet has been not a hindrance but a help to established brokers (US), estate agents (UK), immobiliers (France) and other residential property sales specialists around the world.

Before, the only places they could advertise client homes for sale were the classified sections of local newspapers. The web, by contrast, offers access to many more people in a variety of places and, crucially, the ability to search for homes within a defined set of parameters: number of rooms, exact location, price.

Property search websites – Realtor.com in the US, Primelocation.com, Propertyfinder.com and Rightmove.co.uk in the UK, Idealista.com in Spain, Seloger.com in France, Immobilienscout.com in Germany – now serve as advertising aggregators, working hand-in-hand with agents and developers and bringing them business. Idealista, for example, has 1m unique users, charges €135 a month for agency listings or €295 to developers with new projects and reported pre-tax profit of €1.6m last year. Added services provided by these companies include text messaging and e-mail alerts. Primelocation, which now has more than 2,350 member agencies in the UK and abroad, sends more than 4m of the latter to registered users each month.

Other companies are focused on providing information and improving market transparency. Zillow.com, a US company based in Seattle, allows users to zoom in on satellite imagery of neighbourhoods, then offers “zestimates” and other details on 67m homes, whether they’re for sale or not. Reactions on internet bulletin boards range from “wow, just put in our house and it’s exactly $1,000 off from what we appraised at last week” to “the prices listed on my street were 30 per cent to 50 per cent off what homes are actually selling for”.

Ononemap.com in the UK offers searchable street maps of neighbourhoods with most of the homes for sale or rent plotted as little red Monopoly-style houses. Click on the icon and you’re directed to more information and estate agent details, which are input automatically for no fee. Founder Philip Sheldrake, another eager 35-year-old, says he set up the site, which covers up to 500,000 homes, or about half the total UK market, as a sideline to his day job not to make money but because he wasn’t satisfied with existing sites. “It’s a very intuitive way to search,” he says. “People love the way they can scroll across the map and the houses pop up automatically.” He wants to help both buyers and agents, and many of the latter have asked him to help improve their own sites.

Increasingly, however, property-focused websites are out to undermine the traditional agency model. Online brokerages promise lower commissions – a flat $2,000 fee in Redfin’s case, compared with the typical 6 per cent (or $60,000 on a $1m house) split between the buyer and seller in the US. Commissions in the UK are about 2 per cent and paid by the seller.

Meanwhile, self-sell sites, such as Cutthemiddleman, aim to do just that. Probert, a beauty salon owner who founded the company after wondering why an agent was collecting £6,000 for the relatively easy job of selling her house, will charge clients £20 a month to advertise on the site. Binstock at Auctionyourproperty takes £50 from sellers who want to register on his site and have a one-day online auction and has already signed up several hundred people.

The next step might be not only facilitating no-fee or low-fee transactions online but also generating them. Redfin is trying to employ technology already used by Igglo.com in Helsinki that allows househunters to pinpoint a property not on the market and make a bid for it. An owner who might not have planned to sell can look at an offer and decide to cut a spontaneous deal.

Kelman admits this particular feature might not work. “We estimated that if you cold call people and say ‘are you interested in selling?’ less than 5 per cent are likely to respond.” But he’s confident that his company’s overall goal – facilitating low-commission, agent-free transactions – is achievable.

This will, of course, mean overcoming several hurdles. In many US states, for example, property industry regulators must be former or active real estate brokers. According to the Consumer Federation of America, they are therefore predjudiced against online-only agencies. “They take few or no steps to foster price competition, protect non-traditional brokers from discrimination [or] educate consumers about how the marketplace works,” the group said in a report this summer.

Perhaps the biggest challenge, however, is gaining critical mass. Kelman now has plans to open Redfin offices in southern California and on the east coast after securing $8m of financing in May from Allen’s Vulcan Capital. But he is a long way off trying to service the whole of the US.

In the UK, many self-sell websites survive by funnelling clients on to larger sites, such as Fish4property.co.uk, which have enough properties to sustain people’s interest. Spain’s Idealista also accepts ads from individual sellers. Yet other popular websites have banned non-agency clients. “The market has changed and we are currently reviewing the policy [but] Primelocation has not accepted online agents in the past on the grounds that their proposition was regarded more as a competitor than as a customer,” says chief executive Ian Springett.

“We can’t risk a boycott from our clients. It’s a real war,” adds Denys Chalumeau, the Seloger founder.

Propertyfinder used to accept non-agency advertisers but told them they were no longer welcome earlier this year. “We don’t want to encourage the growth of something which could ultimately undermine us,” says one agent, who asked not to be named. “People may think we are morons but we aren’t.”

Another way estate agents fight back is by claiming their service is simply better. The typical seller of a home – aged between 25 and 45 – is far too “time-poor” to do the legwork that the process entails, says Mark Anderson, managing director of Hamptons Residential, an old-school agency. Hours can be spent photographing and measuring the house and showing potential viewers around.

“A good agent is able to secure first-class marketing, offer expert advice, consider the best target market and spot any obstacles which could scupper a sale,” Anderson says. “A website could be compared with a bad restaurant, where you come out feeling you could have done it better yourself, whereas with a good restaurant you do not mind paying the price for a better experience.”

The dangers for the dot com newcomers are illustrated by the failure of ­Easier.com, an agent-free property website that six years ago floated in London and was valued at £85m. Although it attracted thousands of homes for sale, it eventually folded. “With hindsight we were too early,” says founder Steve Rist. “We did it right but didn’t have enough cash.” Since Easier.com crashed and burned, he argues, consumers have become more comfortable using the internet.

He predicts that it is only a matter of time before traditional estate agents are forced to close shop or change their business models, especially now that two large UK supermarket chains, Tesco and Asda, are carrying out pilots of online estate agencies. Asda, owned by US giant Wal-Mart, has promised to cut commissions to just 1 per cent while providing all the usual agency services. First off the blocks with a pilot trial in 21 stores, the company believes this has not been done before in Europe or the US.

“The likes of Asda, Tesco – and maybe others like Marks & Spencer or Ikea – have the brand and the branch presence to really shake up the market,” Rist says.

For those with no great love for the industry – “I hate estate agents” gets 6.7m hits on Google – this is not before time.

Additional reporting by Mark Mulligan and Delphine Strauss