I want to buy a

The car is worth about AED 32.000 if the car is neat and everything is working. Check if the EAS (but lot of RR have replaced air suspension with coilsprings) is working well and the remote central lock as well. Most private sellers provide you with Full Service History. The engines have here harsh time due to dust and sand, oil and filters need to be replaced more frequently than elsewhere.
The dealers will try to sell you the car for about AED 50.000 with warranty, which doesn't mean here much. Try to buy the car from someone you know, there is less chance he will screw you. And the maintenance is expensive if the car is not in warranty any more, if you know what I mean ;) ( Once thay wanted to replace my dashboard when one of my LEDs wasn't working )
SOLUTION: Do not buy this car and certainly not without warranty unless you know what you are doing.

If you are buying the vehicle from a dealer then they should give you a guarentee on the vehicles condition.If you are buying the vehicle privately then i suggest taking the vehicle to a dealer for them to advise you on costs and repairs needed.If you are purchasing the vehicle at a good market price then it may be worth while spending a little money getting it reliable.