Honestly .... It all depends on ur lifestyle ... what u r earning could be enuff or too little depending on ur taste.

Is accomodation available for 4 - 6 k (Yes but it will be a studio like wisefool mentioned or a shared F/F Flat or Villa. By the way Doha isnt very big so u dont really have to live in westbay.. there r other good residential areas too). If it is a furnished apt then normally TV and other utilities would be available.

The only provider for Internet would b Qtel and they r ok and offer upto 4Mbps speed for abt QR 400. Not the best connection but its ok for now ... i am hoping other international players enter this market soon. Mobile ditto ... very expensive.

Car ... u could rent or buy a car (4WD) for around 2500 - 3000 QR per month.

Cheers !!