Teaching English

You might like to consider the Peace Corps as they are established in Madagascar. They will teach you the local Language first and do several seminars about Madagascar before you arrive.   
If possible I recommend a vacation here for 90 days and do ground zero research.

For example what do you get for your rent, many cheap rents offer outside showers and community toilets, squat toilets.   Outside kitchens as well that cook off of charcoal and sticks. Gas tanks are available but expensive, about $30  dollars a month 

English is important but not encouraged in this country.  So it would be difficult  but not impossible to find a English teaching job. As to a comfortable living standard I would say you would want at least $1000 dollars a month with expenses included.  Good Luck amigo

P S I also met a young girl of 25 who traveled around the world and was able to secure a place with a religious organization that paid a few dollars and supplied all paperwork but on her own savings she traveled around Madagascar.  Interesting part was that English was not her first language but she knew enough to teach English at the Church School.