how to make a content type that ties to the user and user can only add one?
Instead of creating content types, I think you're better off using the profile module.

For Drupal 8 use the Profile Module


  The Profile module provides configurable user profiles.
  
  Multiple profile types may be created via the UI (e.g. a general
  profile + a customer profile), whereas the module provides separated
  permissions for those. Optionally, profile forms are shown during user
  account registration. Fields may be configured to be private - thus
  visible only to the profile owner and administrators. Profile types
  are displayed on the user view page, and can be configured through
  “Manage Display” on account settings.


Formerly known as Profile2 in drupal 7. Here is a video tutorial. Perhaps it's similar in Drupal 8?