How does it work with financial co-sponsorship? Can a family member or a close friend co-sponsor a fiancee?
Anyone who is a US Citizen or green card holder can co-sponsor affidavits of support .
K-1 visa holders are limited to a single entry. May a K-1 visa holder nevertheless take advantage of automatic visa revalidation?
Yes. U.S. Customs and Border Patrol (CBP) indicates that there is no law or regulation that precludes K-1 visa holders from benefiting from the automatic revalidation provision, provided all entry requirements and criteria are met, and their K-1 status has not changed since their initial K-1 admission.