Kabayan, the salary might not commensurate to the cost of living here and plus the fact that the salary will not allow you to bring your family here in Qatar. And although it's a free accomodation, you being a professional engineer migh tfeel bad once here (and migt start comparing your package) to others that get much higher/better remuneration.

try and wait for a much better offer, if you can afford and if you have the time and resources. Goodluck!