Affiliates play a role in your club, and many clubs require affiliation for a larger body, or even for insurance purposes.
If your club has external affiliates, then you should consider capturing this information during the membership signup process. It may save you a great deal of time later. Identification may need to be verified; it might also be a requirement that the new member signs up to an affiliate before joining your club, (this is often the case for 3rd party insurers).
So if you are going to be working with affiliates, consider the information you need to capture from the beginning rather than later when data entry is problematic.