US Domicile for i-134

[Ann&Paul 0]

Hey everyone, first of all I wanted to introduce ourselves to this great community. My fiancee and I have been reading this website and forums for hours and hours for the past week and it has been extremely useful. We just love how helpful and interactive the community is here, it sure seems everyone understands what a difficult and sensitive situation everyone is going through.

My name's Paul and I'm an american citizen and have been living in Argentina since the age of 10. My fiancee's name is Ann, an Argentine citizen, we have been together for 5 years. We plan on moving to the US and start our family and future there. In order to do so in a timely manner we chose going the K1 route. After researching this for hours and hours we still have a few questions that hopefully someone can help us with.

Affidavit of Support (i-134): Seeing as I haven't been living in the US for 15 years, of course I cannot fully sponsor my fiancee. But it seems that we can use a co-sponsor to cover the financial aspect. But as the main sponsor I still need to have a US domicile which I currently don't have. I am planning on moving to the US and getting a job before my fiancee arrives but I would like to stay with her in Argentina during the process as long as possible. Here comes my question, at which step of the process do I need to have a US domicile? Can I do it after the case is received by the Embassy from NVC, the moment we need to complete the Affidavit of Support (i-134)? Or does the domicile I end up using have to be the same as the one I complete at the beginning of the process in the i-130 form?

That would be our main concern but we also have a few other minor questions.

* Does the co-sponsor need to live in the same city or state?

* I am an american citizen not through birth but from my mother, I have a US passport and SSN but I don't have a certificate of citizenship. The Affidavit of Support asks for this number, is it required?