Immediate Relatives. Relatives of U.S. citizens are immediate relatives if they are spouses, children under 21, or parents of the U.S. citizen. There is no wait to file for IR visas.
Preference System Relatives. Other relatives are classified under the preference system.
1st Preference: Unmarried sons and daughters (over 21) of a U.S. citizen.
2nd Preference: [2A] Spouses and children (under 21) of a permanent resident.
[2B] Unmarried sons and daughter (over 21) of a permanent resident.
3rd Preference: Married sons and daughters (over 21) of a U.S. citizen.
4th Preference: Brothers and sisters of a U.S. citizen.
The Immigrant visa petition (I-130)
The immigrant visa petition for an alien relative can be filed at any time. The Petitioner must show proof of U.S. citizenship or permanent residence and documentary evidence of the qualifying relationship to the Beneficiary. If the relative being sponsored is an immediate relative and is in the U.S., the relative petition and the Application for Permanent Residence can be filed together.
The Appication for permanent residence (I-485)
For a Preference category petition, once the Relative Petition is approved, the Application for Permanent Residence can be filed if visas are available. Visas are always available for immediate relatives of U.S. citizens. Beneficiaries under the preference system must wait until visas are available. The date of filing the petition establishes the "priority date" which is the Beneficiary's place in line for their visa.
At the time the Application for Permanent Residence is filed, the Beneficiary can apply for work authorization and permission to travel outside the U.S. while the application is processing.
Final review, interview preparation and USCIS interview
When the case has been scheduled for the USCIS interview, complete a final review of the case to ensure the case has been filed correctly and amend or prepare a supplement for the filing.
Marriage: If the relative petition is based on marriage, at the time of the interview, if the Petitioner and Beneficiary have been married less than two years, the CIS will grant the Beneficiary conditional permanent residence. The Beneficiary must file a petition to remove the conditions (I-751) 90 days prior to the two-year anniversary of conditional residence.
Approval or Request for Evidence?
Please note that if your permanent residence is approved at the interview, it will take some time for you to receive your Permanent Resident Card. The Service is not required to give you any temporary evidence of your permanent residence. We advise you to wait for issuance of the card prior to making any international travel plans.
If your case is not approved, its generally because the USCIS officer needs more information and will issue a Request for Evidence and will let you know how long you have to comply and turn in the requested evidence.
After responding with all requested information, the officer will generally approve the case and will notify you of the decision.