Depends how your life style is. Normally a decent single bedroom house these days will cost around 3000 - 3500 QAR and a double bedroom from 4000 - 6000 QAR, depending on area and other features (furnished, unfurnished, semi furnished). As far as the food is concerned, if you cook at home, it wont cost more than 1500 (max).

Medical is covered through medical card provided by government. Rest You can make a decision. But still 12k sometimes feel a bit on the lower side, as the rents are getting higher and higher everyday.