I am a brand new citizen and I am filing papers to bring my parents from England to NY to live with my husband and our four children. As I understand it once they get their interview and medical stuff out of the way, and get their visas do they enter as Legal Permanent residences?
They will enter the USA as permanent residents. The duration of the immigrant visa is stated on the visa stamp (I think it will be 6 months) and they must enter the USA within that time. They can come and leave after they get their green card in the USA. Read the instructions on the Form I-131 for reentry permit if they expect to be gone for 6 months or more.