I just came to Qatar with my 86 days old baby.You can bring your baby before 90 days without the Visa. No salary or other questions are asked. Show the the passport of your Baby with the orginal Birth certificate .(In my case they didnt even asked the birth certificate). Then immigration officer will grant 30 days Visa for your Baby. In that time apply for permanent visa.
its very very simple.
Take care and good luck