USCIS specifies that only conditional permanent residents who obtained their status through marriage can file Form I-751.
Who may file Form I-751?
USCIS specifies that only conditional permanent residents who obtained their status through marriage can file Form I-751. After approving your Form I-751 petition, USCIS will remove conditions on residence, and you will obtain a 10-year green card. A dependent child of a conditional permanent resident can also file Form I-751.
Conditional permanent residents should apply Form I-751 jointly with their spouse provided they are still married to him or her. They should file Form I-751 with additional documents.
If you became a conditional permanent resident as an investor, you must not file Form I-751 to USCIS. Use Form I-829 instead. http://www.breakingpropertynews.com/newsr/8602
Why does USCIS grants only two-year green cards to married immigrants?
USCIS wants to verify whether an immigrant is lawfully located in the United States after a marriage with an American or a lawful permanent resident. Because many immigrants want to more rapidly acquire U.S. residentship and citizenship, they may fraudulently marry to a U.S. citizen or resident. Therefore, USCIS grants only two-year green cards to married immigrants to simply fight fraud.
When a conditional green card expires, a conditional permanent resident must file Form I-751 to USCIS. After that, the resident must attend an interview at USCIS office. USCIS will then decide whether such an immigrant earned the right for lawful permanent residentship.