and unfortunately, the beast is the unregulated market in Qatar. There are now MANY landlords who are refusing to pay any commission to agents, and this has therefore led almost EVERY main agency in Qatar to start charging tenants. In THEORY, they should provide you with a great, professional service, though admittedly this is not always the case.
The UAE has a regulatory body in place....but tenants pay 5% there in fees for EVERY deal! Often the service is terrible there, even with the laws in place.
As has been said, it's a one off payment.
Unless you have the time to trek around Doha looking for a commission free home,stick to the main agents(NOT THE INDIVIDUAL ONES!)and make them work!