I am a USC. My husband and I are going through I-485 process now. Biometrics appt. next week. He is not seeking citizenship, only PR. His mother is currently in the US on a work visa. How long after he receives his initial green card (after immigration interviews) before he can begin the process of applying for her to get PR. Or would it just be better for me to apply for her as well? Thanks very much for your help.