For illegal immigrants, they can apply for GC after 5 yrs. That doesn't mean they will be approved. They probably will go throuh the lowest EB channel, which might still take over 10 yrs for them to get one.
For us, legal non-immigrant visa holder, like H1b or F1, we can apply as soon as we arrive. Though the EB based still takes a long time.
For us, legal non-immigrant visa holder, like H1b or F1, we can apply as soon as we arrive. Though the EB based still takes a long time.