He can file for US citizenship, if he is otherwise qualified; the fact that he is unemployed will not be a factor in that process. To petition for you, however, he will either need to show an income sufficient to sponsor you for affidavit of support purposes or have a joint sponsor (friend, relative, co-worker, neighbor-ANYONE who is a US citizen OR green card holder) whose income is sufficient and who will be willing to sign the affidavit of support on your behalf.
Answered on May 29th, 2012 at 1:21 PM