I taught in China for 8 years, all with a Z visa. You cannot get a Z visa legally without evidence of invitation to teach in China. That must be on a piece of paper sent to you and also given the official government stamp. After you arrive in mainland China, you still must get a health check by a Chinese hospital and also be processed in person by the local police station nearest the school you work at. Usually, the rep from the school with go to the police station with you, but you must bring your health check to that appointment. So, if anyone got a Z visa in HK, it was only by having that invitation to teach and after that, they still had to be processed by the police. If someone says otherwise, you will hear many tales here and there, but overall, quite contrary to the truth. To get a business visa, you must have invitation to work for that company with official stamp also, which is called an F visa. Otherwise, you can get a tourist visa in HK somewhat easily, unless you are returning to China over and over. They are cracking down on that pattern now, as of 2014, and many people are not being permitted to get a new visa in HK, as they once did easily.