The sponsor/co-sponsors would have to (generally) sign the I-864 Affidavit Of Support. This is a contract between the sponsor and the US government, promising that the immigrant won't become a public charge (basically won't go on welfare). They are effectively promising to, if needed, provide support up to 125% of the Federal Poverty Level. Think along the lines of $1100/month.

It used to be that only the government would seek reimbursement from the sponsor if the immigrant did become a public charge, but since 2005/6 there have been an increasing number of lawsuits against sponsors and none - as far as I'm aware - have gone against the immigrant. The I-864 is also being used during divorce cases to calculate spousal support even in cases where ordinarily no spousal support would be ordered (for example, for a short marriage).

The obligation does not end until one of these conditions is met:

1. The immigrant dies;

2. The immigrant leaves the country permanently (abandons their residency)

3. The immigrant earns 40 qualifying SS quarters (works for around 10 years)

4. The immigrant naturalizes (becomes a US citizen).


This is a very serious commitment. And unfortunately most sponsors don't realize the gravity of the potential obligation.