It should take anywhere from a few weeks to several months. If what you responded to was an initial RFE and you submitted what they requested, the next step will be an interview.
Reasonable time from the day they get the RFE
NYC EXPERIENCED IMMIGRATION ATTORNEYS www.myattorneyusa.com; email: firstname.lastname@example.org; Phone: (866) 456-8654; Fax: 212-964-0440; Cell: 212-202-0325. The information contained in this answer is provided for informational purposes only, and should not be construed as legal advice on any subject matter.