What is the cost for American citizens to apply for parents' immigration? Apply for the fee of 2 people.

if the parents of American citizens are outside the United States, their children can apply for i-13 first, and the materials to be submitted include American citizenship paper, birth certificate (father's name is required), parents' marriage certificate, etc. After i-13 is approved, wait for the notice from the American visa center, then prepare the financial guarantee and apply for an immigrant visa. After the immigrant visa is passed, you can go to the United States for permanent residence.