how long a green card holder stay outside the us and be allowed to return
In general, a lawful permanent resident is allowed to travel outside the U.S. for a period of up to one year without any special documentation other than his green card. If the lawful permanent resident applies for a Re-Entry Permit prior to departing, he will be eligible to depart the U.S. for up to 2 years â just so long as he is in possession of the permit prior to reentering.