Well, $20,000 per year is enough if it is just him and her. He just has to prove that he makes about that amount, maybe a little less and he does not need a Joint Sponsor.
He has two ways to get her here and neither is quick:
1) The K-3 spouse visa takes 6 to 9 months. The I-129F will cost $340 plus $420 for the I-130, and $350 for the visa processing fee. Then after she enters the U.S., she must still file the I-485 for $1070 and wait for the marriage interview about 5 to 7 months later.
2) The CR-1 visa (or IR-1 if your marriage is more than 2 years old) takes about 1 year or so. The fees are $420 for the I-130, $330 for the visa processing fee, $88 for an Affidavit of Support fee. But once she enters the U.S., she enters as a Resident and she does not have to file (or pay for) an I-485 nor does she have to attend an additional interview. She just gets her green card in the mail a few weeks later.
So the K-3 is faster but generally more expensive. The CR-1 (and IR-1) are slower, but generally cheaper. And no, there is no middle-visa that she can use to enter the U.S. while that process is pending. She will most likely have to wait outside.
Here is a link to all three:
So IF he filed a K-3 for her in March, she MIGHT be able to get into the U.S. by September, but I think it highly unlikely. Even if she were to have the baby outside, the baby will be able to immigrate and receive U.S. Citizenship.
And here is a link to how much he has to make where you would look at the 125% column:
IF he does not make enough, then he will need to find a Joint Sponsor to also file an I-864 along with his I-864 and that Joint Sponsor can be any U.S. Citizen or U.S. Lawful Permanent Resident that makes enough money and is over 18. It does not have to be a family member nor household member.
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