Affiliates play either a small or large role in your club depending on your type of sport.
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 will save you a great deal of time later.
This can be in the form of an id and affiliate name, it might also be a requirement that the new member signs up to an affiliate prior to 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 will be problematic.