Nidenel:
The short answer is: DO NOT ACCEPT.
The company is real and they have a fancy building in one of the main commercial streets. But, from what you have told, I bet the owners lack of scrupulous and are using deceiving schemes to maximize their profits.
The salary they are offering you is the minimum legal wage. Most Chileans won't work for that money and an average teacher's salary shall be around $1,000. I am also skeptical about the lodging and living expenses they will cover. Considering they are cheap thinkers -from what they are offering you- most probably scenario is you will be living in a boarding home, in a poor -and therefore unsafe- neighborhood.
To give you an idea what $200 mean -Chile's cost of living is similar to that in the U.S.- You will be way below the poverty line -even for Chilean standards which are lower than those in America- Just commuting to your work will cost you $75/month at a minimum. A sandwich with a soda $10. Just a soda $2. Each bus ride $1.5 -if you don't have to transfer. Getting into a nightclub $10 to $15 and $6 to $15 for the drinks inside. You will struggle to make it to the end of each month, if you are able to make it whatsoever.
The certificate you are pursuing, probably is as valid as anyone I can print for you in my laptop for free. Just being sarcastic here. But I bet there are better ways to get a decent certification with better incomes. Try contacting some of the local universities or more reputable institutes (the local American Chamber of Commerce -Amcham Chile- or the British-Chilean Institute may help you)
Native English Speakers are ESSENTIAL in marketing the business and they are in good demand. These guys are just trying to get that cheap. Cost of translating documents $10/page minimum. Cost of a private English tutor $20/hour minimum. And these are pricing hiring directly, if you get the services through the institutes, they will charge double or more. How much are you getting per hour? They can legally make you work 48 hours per week. Make your own maths.
Finally, what if they don't return the deposit for whatever reason. What are you going to do? Even if you live a monastic life, don't go out, just work, eat and sleep, after expenses going to work and buying materials, in the 6-month you will have much less than $500 in your pocket. I bet you will loose your money and end working for free.
Wish you luck and stay away from them!