There are more "real" toys, such as tin frogs, shuttlecocks, Chinese ring puzzles, 3D five-in-a-row, cola ball (in which one attaches a string to a soccer ball, and the player can hold two ends of the string in hands to control the ball while kicking it), touhu, an ancient game first popular in the Warring States Period (475-221 BC), sees players throw arrows into a flagon, spinning tops, indoor golf and so on. The prices range from 2 yuan (31 US cents) to 500 yuan.

Song carefully selects these toys from about 3,000 toy producers in China that mostly are targeted at children.

"Parents and grandparents are willing to spend much on toys for kids, but when it comes to elders, they are used to living thrifty lives so that they are unlikely to buy expensive toys for themselves," Song says.

He recalls an old man trying to bargain the price of an automatically rebounding table tennis ball down.

"It has a base, a flexible steel stick and a ball, selling at only 35 yuan. He said that he only needed the stick and asked me to cut the price," he says.

"If the cost of a toy is one yuan, and if it's for kids, the price may be 10 yuan or even 20. But if it's for elders, it might be priced at 2 yuan and it's not bad if you can sell it at 1.5 yuan," he says.

Apart from prices, another important thing that makes selling toys to elders difficult is that the toys must be safe.

"We must make sure that the susceptible users won't get hurt by the toys," he says.

Song, from Northeast China's Jilin province, came to Beijing in 2004 and tried to start a business, but failed, so the next year he joined in an advertisement agency.

He got the idea to sell toys to elders in 2009, when he was working for a show on China Central Television targeted at this group.

His work required him to understand the physical and psychological needs of elders. However, he found among his clients, eight out of 10 were in the healthcare industry.

"Healthcare products (such as bird's nest) are nearly useless but expensive. If we can provide elders with entertaining toys that they can either play happily on their own or with other elders, they will enjoy a better life, which cannot be achieved by taking in healthcare products or medicine," he says.