Once you turn 21 years, you should file a Form I-130 petition for your mother. To avoid unnecessary delay, prepare the application and have all supporting documents and fees ready. On your 21st birthday, submit the application with CIS. The I-130 should take about 8 months to approve. Thereafter, contact the National Visa Center for processing of your mother's immigrant visa applications. She will be called in for interview at a US embassy in Mexico.
Answered on Apr 16th, 2013 at 9:19 PM