Rob Mitchell said
1 year, 1 month ago: @melissaholmes Secure login is a matter of having a website backed by a database for members to create/login and the pages that involve personal information should be protected with SSL certificate.
This is all quite do-able but it sounds like you’re looking for a solution that’s already implemented for calendaring (shared?) and registration/checkout payment, right? I’m a custom guy so I just write this stuff myself. Not sure if BigCommerce.com could handle most of what you need.