NAHI - National Association of Home Inspectors
Professional Home Inspection Institute is affiliated with NAHI, the National Association of Home Inspectors. NAHI is one of only a few non-profit home inspector associations in the US. They offer members a standards of practice and code of ethics to follow as well as giving inspectors a nationally recognized credential for marketing purposes.
PHII can give you more information about joining the National Association of Home Inspectors after you've completed the courses (including information about taking the NAHI exam and how to sign up with NAHI, pay their fees, and satisfy continuing education requirements)