Good question. I was expecting it.
A 2-bedroom apartment will cost you around QR 4500 with water and electricity. Initially, you will need to furnish it but this is just a one time cost. You could get it furnished in say QR 5000 and cost will be lower if you go for second-hand items. You will find such items on sale at Qatar Living. But you need to be careful buying electronic items. If the apartment has Aircons, well and good. Some of them have but most of them don't. You will need QR 3000 for two new aircons. Your monthly expenses for food expenses for you and your wife will be around QR 1000. Add another QR 1000 for other miscellaneous expenses such as internet, petrol etc.
The rest is ALL in your pocket.
However, your savings also depends on your own life style. If you go to clubs or dine and drink frequently, it is totally a different story.