Once an NVC visa is available, the processing time is about 2-3 months. The U.S. Department of State website outlines that NVC processing entails the proper submission of all correct forms and fees, completion of a consular interview, and receipt of passport and visa in the mail.
If the petitioner is a U.S. citizen and the beneficiary is a spouse, unmarried child aged 21 or younger, or parent of a citizen aged 21 or older, a visa is immediately available, explains the U.S. Department of State. They could start NVC processing immediately. All other applicants are subject to a wait time based on the priority date assigned to them.