You must be a US Citizen (older than 21) to sponsor your mother.
You cannot file as a Legal Permanent Resident.
Once you become a Citizen and file the process takes about a 6-10 months.
Step 1: Wait until you can apply for naturalization.
Step 2: Apply for naturalization.
Step 3: Become a US citizen
Step 4: Petition your mother.
J Charles Ferrari Eng & Nishimura 213.622.2255 The statement above is general in nature and does not constitute legal advice, as not all the facts are known. You should retain an attorney to review all the facts specific to your case in order to receive advise specific to your case. The statement above does not create an attorney/client relationship. Answers on Avvo can only be general ones, as specific answers would require knowledge of all the facts. As such, they may or may not apply to the question.