Your friend in Beijing is right. This is NOT what most legal, certified English teaching companies do. There are so many red flags with your situation that I would recommend just cutting your losses and not go to China to work for these people.

The first red flag is that they are hiring an 18 year old who seemingly has no bachelor's degree or teaching certification (TEFL, CELTA, etc.). This is illegal in China. To teach English, you would need at least a 4 year bachelor's degree (in any subject, but preferably English or education related) and a teaching certification. Post-graduate work experience is required by many schools as well, but from my observations, this requirement is on a case-by-case basis depending on where or who you are working for. Any reputable recruiter would tell you that you need a Z visa, and nothing less, to work full time in China. It is for this reason that most schools that are certified to hire foreign teachers won't consider hiring anyone younger than 21-23 years old.

Why is this important? Not only can you be deported, fined, and banned from the country if you're caught working illegally without a Z visa, but companies and schools can, and most likely will, screw you over at their earliest convenience because you DO NOT have a legal contract that can be enforced. There are plenty of stories online of people who were abused and screwed over by their employers because they didn't have a legal Z visa. Believe me when I say you do not want to be one of those people.

Don't take this the wrong way, but please stay home for now. If you really want to be an ESL teacher, go to university and get a bachelor's degree. Not an associate's degree. A four year bachelor's degree. That's the ONLY way to secure a legitimate teaching job not only in China, but in pretty much any East Asian country (including South Korea and Japan, if you ever become interested in those countries).

I'm not saying this to be mean, or to discourage you from travelling abroad or eventually working as an English teacher. I'm telling you this because you are putting yourself at great risk working for these people, especially since this is your first time in China. China can be a wonderful place to visit, live, or work, but you have to go in with your eyes wide open.