How can I build a subscription product selling system with drupal commerce
Check Commerce subscription products module.


  Features
  
  
  Sell subscriptions via products.
  Administers can view and customize the subscription validity per user    if they have necessary field permissions.
  There are two "rule sets" (Subscription starts, Subscription ends)    that make customizing the subscription easy, e.g. one could    easily    add rules for granting/removing a user role.
  Subscriptions expire automatically once the validity time is reached    thanks to the Rules Scheduler (requires cron to function).
  Views integration, as the subscription validity date is implemented    as account field.
  Custom notifications like "Warning: Subscription expires in 2 weeks"    can be easily configured using Rules and the Rules    Scheduler.