Usually and based on my own experience I had maximum 30 days after issued to enter Qatar and while paperwork was being made my Entry permit was 3 months valid (which is similar to a 3 months probation period). Once you get into the country the company you work for should take you to medical comission and then to police authorities in order to get the RP (residence permit), and after that you can get driving license, credit cards, bank loans, etc etc etc.

Best of luck