As a green card holder, you cannot directly sponsor a friend for immigration. Family-based sponsorship is limited to specific relatives like spouses and unmarried children. Any path for your friend would likely need to be based on work, study, or another independent category.

One option is helping your friend explore employment-based visas if they have skills in demand. You can support them by making professional introductions or guiding them through the process.

Another possibility is a student visa if your friend plans to study in the U.S. temporarily. If they later qualify for a work visa, that could open a longer-term pathway. You can also help by providing housing support or financial affidavits where permitted. It is important to avoid informal arrangements that could violate immigration rules.