what is your nationlatey, how old is your mother, if she is above 60 years old, you have to get a special approval from the autharised officer at the immigration departmant that your wife is not in the country or you are not marrage with the application form typed in Arabic she will visit you only after you get your after your resident permit with cetificate from your Embassy to approve that you are the only son of your mother attested from ministry of foreign affairs and salary certificate and labor contract attested from labor office,you will get visit visa for one month extendable for anther 5months after she arrive to Doha with appliction and visa copy and 2 photos passport size, it will cost you
200 first entry for one month
100 medical examination fees
1000 for the extension of 5 months
she has to stay out of the country 90 days to apply again with the same doucment copy