My concerns are pretty much summed up in the title. I'm building a site that may provide sensitive information to customers. Can turnkey membership be set up using business catalyst? Auto-renewal capabilites?
If requiring special membership to gain front-end access to your site you can use secure zones + recurring billing to require login prior to accessing various pages within your site.
If requiring for back-end admin access we don't have a module because this would require you to upgrade your site plan to allow for additional users to gain admin access. You would first need to purchase additional users via portal -> clients -> details if required.
FAQ: http://www.adobe.com/products/business-catalyst/faq.html (billing -> what extras can I add?)
Hope this helps!
Europe, Middle East and Africa