美宝作为美国公民，为成年父母申请绿卡，属于Immediate Relative，有最高优先级，并不需要排期。
美国公民与移民局（USCIS）官网说明：Green Card for an Immediate Relative of a U.S. Citizen
If you are an immediate relative of a U.S. citizen, you can become a lawful permanent resident (get a Green Card) based on your family relationship if you meet certain eligibility requirements. You are an immediate relative if you are:
To promote family unity, immigration law allows U.S. citizens to petition for certain qualified relatives to come and live permanently in the United States. Eligible immediate relatives include the U.S. citizen’s:
The spouse of a U.S. citizen;美国公民的配偶;
The unmarried child under 21 years of age of a U.S. citizen; or 未满21岁的美国公民未婚子女
The parent of a U.S. citizen (if the U.S. citizen is 21 years of age or older).美国公民的父母（如果美国公民年满21岁或以上）。
Immediate relatives have special immigration priority and do not have to wait in line for a visa number to become available for them to immigrate because there are an unlimited number of visas for their particular categories.
I-485表格的申请，永久居留申请或调整状态申请（PDF，545 KB）
因此美宝为中国父母申请绿卡，要满足两个条件：
1.美宝年满21周岁
2.美宝纳税满两年，且报税收入大于当地贫困线125%（2019年联邦贫困线 经济担保须以最新联邦贫困线为准）。加州三口之家2019年是26663美元。
当然如果美宝此时没有工作没有报税（这个年龄一般在读大学），可以找一个人担保。担保人满足报税条件即可。
美宝为父母申请依亲移民整个流程大概需要10-12个月。
