I think Uranus has given you some good rules of thumb to work by.
Having said that, the pay could sometimes be a little less than what he suggests, depending on the industry you work in. (For example, the hospitality industry doesn't give one higher salaries (I'm talking only about large international companies) just because one takes a Middle East transfer.)
However, it has to be at least the same as your salary back home, if you want to have a similar lifestyle as well as put something aside. Or a little more, if you still ahve tax considerations to deal with.
Doha is NOT cheap if you want to live well.

You might just get a decent flat for 9,000, but I hear that prices go up in March-April annually because of school terms.
But note that I said 'decent'. For very nice in a good locality, it would be 10,000 and up for 2 bedrooms. We just finished a flat-hunt yesterday, hence I know :)

I know of a couple of people who rent a car for 1200 a month (mid-sized SUV).
In the long run, if you plan to be here a couple of years, buying a car is the best.