Ecommerce Subscription
This answer is based on the tutorial http://www.stonemind.net/blog/2008/02/07/tips-for-implementing-a-subscription-based-drupal-site/.
Here is further information in EC subscriptions:Role products
http://drupal.org/node/88239

Firstly the user needs to install various modules


All modules in the E-Commerce Core package.
Your payment gateway choice.
Generic Product
EC Recurring.
EC Role.


It is important to note that subscription are intangible. They are not solid objects and therefore don't have an arrival time. For this reason the type of product is a "Non Ship able product"
E-Commerce configuration (at /admin/ecsettings)

The tool mentions that the way rebelling is achieved is due to the cron tasks. So therefore its imperative that is can be achieved.

Multiple roles can be purchased to achieved so there can be different types of subscriptions. To enable only certain users to access  certain content the node option premium module.  http://drupal.org/project/nopremium. This is the replacement for the module premium that was used in drupal 6.

If you want different types of roles to be only able to see a teaser. You can use the contemplate module to achieve this task. This means that you could have content that certain users will not be able to see. A good example is news site which give a teaser and ask you to register to find out more information. 

http://drupal.org/project/contemplate