Economists say the first five years of the 21st century were the golden age of investment in China's top cities. Investors poured in billions of yuan, creating a sea of opportunity for job seekers, skilled and non-skilled.

But today, to leave or stay has become a serious consideration for many families as young and educated professionals struggle with the rising costs of living in their dream homes, rises fuelled largely by surging housing prices.

With a monthly income of about 10,000 yuan (HK$11,300), Tang and his wife looked for a second-hand apartment of 70-odd square metres priced at 1.2 million yuan, on the fringe of Beijing. But the savings of the white-collar couple and help from their parents were not enough for the minimum down payment of about 400,000 yuan.

'After months of research, we came to realise that home ownership in the national capital is squarely out of reach for those like us,' Tang said.

Tang's decision was simple: he and his wife might earn less in their hometown of Nanning , probably only half of what they made in Beijing, but the average housing price there is only a quarter of Beijing's more than 20,000 yuan per square metre. While the Tangs chose to realise the traditional Chinese dream of owning their own residence by moving out of Beijing, those determined to pursue that dream in the first-tier cities are struggling.

Even though Li and his wife said owning their own apartment gives them a sense of being home in Shanghai, they acknowledge life is not easy.

With half of their 20,000-yuan monthly income spent on mortgage repayments on their 80-square-metre apartment, which cost 2 million yuan, the couple face great financial pressure.

They say that's the main reason they're still childless.

'Still, we are not certain that we can stay here our entire lives until we have paid off our mortgage, which runs for 20 years,' said Li. 'I mean, what if either one of us is laid off?'

New college graduates nationwide try to get relatively high-paying jobs working for the government, a bank, a conglomerate or a Fortune 500 company in those leading metropolises. They hope their incomes can rise fast enough so that by the time they are 30 they can think about buying something.

The term 'ant tribe' was coined by Chinese sociologists to describe the struggles of young migrants who flock to big cities in hopes of a better life but instead have to put up with low-paying jobs and poor living conditions.

The population of Tangjialing village in northern Beijing was 3,000 not long ago, but it has exploded to 50,000 with the influx of new ants in the tribe.

In his book Ant Tribe, published in September, Peking University scholar Lian Si estimates the total population of the 'ant communities' in major cities across China at 1 million, with about 100,000 in Beijing alone.

'Most of them make no more than 2,000 yuan a month,' Lian said. 'They rent a bunk bed for about 300 yuan, have two meals a day, and commute one to two hours to work in central Beijing.'

One young man reportedly staged a protest on board the inaugural service on line 7 of the Shanghai metro. Sporting a tent covered in slogans condemning sky-high property prices, he told sympathetic commuters his tale of woe about not being able to find a wife because he couldn't afford an apartment.

'I don't have an apartment, but I do have a brand new tent,' one of the slogans proclaimed.

Frustration over unaffordable property has even found expression in rock 'n' roll. Playing off the Beijing Olympics slogan of 'Beijing welcomes you', one song has the title Shanghai Does Not Welcome You. Its lyrics depict poor young people being sent packing to make way for luxury houses to be built for rich people - the only ones made to feel welcome.

One of the most talked-about television programmes in China is the soap opera called Snail House, which offers sex, corruption and political intrigue surrounding young people's attempts to buy houses as prices soar.

One character becomes the mistress of a party official to help her buy a flat, while another young couple struggles unsuccessfully to raise the deposit for an apartment in a city that resembles Shanghai. The series struck such a raw nerve that government censors ordered it off the air at the end of last year, but that has not stopped it becoming a big online hit.

Yi Xianrong, an economist with the Chinese Academy of Social Sciences, said housing prices in Beijing and Shanghai had almost reached the levels in New York, London and Tokyo, but average salaries were only about one-tenth as much.

Many low- to middle-income young professionals say buying a piece of real estate is becoming increasingly out of reach. Even most top salary earners say their salary increases can't match rising property prices in the first-tier cities.

Fuelled by low interest rates, prices in Shanghai and Beijing doubled in less than four years before the global financial crisis, and have now doubled again.

The statistics are alarming. According to property agency Knight Frank, the average price for a new home in the year to last November rose by 68 per cent in Shanghai, 66 per cent in Beijing and 51 per cent in Shenzhen. China Daily reported that the ratio of housing price to income was higher in China than anywhere else in the world.

Zhuang Jian, senior economist with the Asian Development Bank China Resident Mission, said the home-price-to-income ratio should be between four and six according to internationally accepted standards.

'But they are commonly over 20 in first-tier cities,' Zhuang said.

A survey by ifeng.com, a news website affiliated with Phoenix Television, suggested that 6,997 of 7,472 respondents (94 per cent) said they believed young professionals should leave big cities and move to second-tier cities to have better lives.

Zhuang said if housing prices continue at current levels or rise further, more professionals will leave.