Building a Membership site in Drupal 8

Memberships are not all the same. Some memberships last a lifetime, others last a year, or a month. Some memberships are for an individual, others for a couple, others for an entire family.

Some memberships are for a particular time period -- the 2017 season, the 2017/18 school year, Summer -- others are for a particular length of time starting when you purchase it.