* Vision Fund to open 1st mainland office in Shanghai - sources. : HONG KONG (Reuters) - The SoftBank-led Vision Fund is hiring an investment team to be based in China as the $100 billion investment giant expands in one of the world’s most vibrant tech markets, two people with direct knowledge of the move told Reuters. The Vision Fund plans to open its first China office in Shanghai next year, followed by Beijing and Hong Kong. Altogether it hopes to hire about 20 people, said the people, who declined to be named as the information was confidential.