English teaching in China is highly fragmented. Unlike other industries where one or a few companies dominate, English teaching in China has many big, medium, small, and micro-companies. Big companies are not necessarily the best paid or best places to work.
Simply because of the balance of demand and supply, many people who can teach English well tend to get more work coming to them through referrals.
English is the common language at both official workplaces such as schools, big companies, and training centers, as well as informally at places like coffee shops that feature English teachers.
For immigration needs, a bachelor’s degree in any field, and a teaching certification (such as a CELTA) is the best guarantee to ensure getting offered an excellent full-time job and a working visa. In general, going to a brand-name school (not an online degree) in a well-known country such as the US, Canada, UK, Australia, and having a respected teaching license is the best way to be viewed as qualified. It is good for you teach in China.