Once you apply for a green card it takes approximately 8 to 14 months to receive the green card.
You must be a permanent resident of the U.S. (aka having your green card) for at least 5 years before you become eligible for naturalization.
Are there any exceptions to the five-year rule? Yes, there are:
Permanent residents who are married to U.S. citizens only have to wait 3 years to apply for citizenship
Battered spouses of a U.S. citizen also only have to wait 3 years
Spouses of U.S. citizens in certain overseas jobs, refugees and asylees all have special circumstances that may permit them to apply for citizenship earlier than 5 years.
On average, for a marriage based immigration process - you’re looking at 6 to 8 years.