Creating a members only section

I am creating a site where a certain portion of it will house documents not available to the general public. I am looking for a way to restrict access that is not BuddyPress. It is not paid or premium content but relatively confidential.

Would like a robust, easy to use registration system that sends email confirmation, is not overly susceptible to spam, and can contain a custom field such as apartment number.

Suggestions? Thank you.