Kabayan.. Everybody's suggestion is correct. I will suggest to you the same. I was working previously for 2years in qatar with the same salary that they offer to you,including free accom, transpo, food allow,to the point including the overtime allowance just to reach a monthly salary of 3K. You can save a very little amount of money, but still not enough to support the people you will left behind in our country.Alam mo naman ang kultura natin, mahirap tanggihan ang pamilya (kaarawan ng nanay at tatay mo,kapatid mo, tuition, pasko, new year,pasalubong etc..). Include also your personal needs and future savings.
Think it before you decide to accept the offer. Based on my experience,even I completed my 2years contract and decided to resign after completion, they will not grant an n.o.c.. Its better you ask your friends also who is already in doha, to know more about the rulings of qatar before your enter the country. Try to re-negotiate or be a little more patient to look and wait for another offer from qatar, since there will be no difference with what ur earning from the philippines.