Teach in China scams have a lot of things in common. First, the company may reach out to you via social media even if you haven't sought them out first. They may seen too eager to hire you, even before having a video interview or asking for your resume. They may offer you an eye-opening salary/perks in spite of your lack of a bachelor's degree, TEFL certificate, teaching qualifications, or teaching experience.
You may be asked to fork out ridiculous placement fees upfront to "cover costs" you have no idea about. They may ask you to enter China on a tourist or student visa ,promising to get you the proper work visa after you arrive. Or, when you land, they escort you to a less than livable apartment or room you have to share with other ESL teachers.
You may also notice suspicious things. For instance, they start you off in the one school then shift you to another without proper reason or cause. You may be offer an ESL "contract" with vague terms. Worst of all, you may arrive in China and realize that there is no actual job or salary waiting for you.
They might also tell you that you'are paid "under the table" or will hire you when you're not on a proper work visa. Keep in mind that even if "your friends are doing it," you are at risk of deportation (and no security for faulty pay or companies mysteriously disappearing) if you are working on a Tourist, Student or Internship visa while in China.
How do you avoid falling victims to these scams?? Simple answer - never work on a non-working visa. Make sure you have all your paperwork done before coming to China. Chinese government only allow legitimate schools/training centers to sponsor a work visa as they go through a vetting process. So by securing a work visa before coming to China, you know you are protected legally and you are working for a legitimate company.