It depends, perhaps not at all. However, the responsibility is not for life. There is a misconception. A U.S. Citizen who marries a foreigner, who becomes a lawful permanent resident, is responsible for a bit longer.
That is, until the now permanent resident spouse becomes a U.S. Citizen, completes 40 quarters of lawful employment, or ten years of lawful permanent resident status, whichever comes first. This means that a U.S. Citizen can be held responsible for supporting the foreigner long after the condition is removed from permanent resident status, as well.
Should the green card holder be unable to support themselves, they can seek support from those who filed the I-864 affidavit of support. A joint sponsor can also be held liable, where the foreigner seeks help during divorce proceedings. The permanent resident can ask that he or she be supported at 125% of the level of subsistence based upon the Department of Health and Human Services charts. This is true, unless it is determined that the lawful permanent resident is employed and earning at least 125% of the level of subsistence.
If you have further question on how the above responsibility can take place or be negotiated, then reasonably consider an appointment or teleconference with an experienced immigration attorney. This situation may get complicated.
The above is general information and does not create an attorney client relationship.
It is useful to review the responsibility of sponsor on the instruction for the affidavit of support on the uscis.gov website.
Better still to contact an immigration lawyer for a consultation to discuss your particular case or be familiar with the immigration process.
It is for a 10year period unless the sponsored immigrant acquires 40hours SS credit or becomes a US citizen.
If the sponsored immigrant has already acquired the requisite 40SS hours you do not need to sponsor him or her.
You are welcome to use the link provided below.