Selling per-node access without creating two entities I want to create a Pay-per-view site under Drupal. 

I followed the instructions of Commerce guys, which combines the use of Drupal Commerce and Content access. 

But this solution means creating two entities: a product display + the paying article. It raises several problems: two nodes with the same name, two nodes as we can comment... 

I would thus want only one node, with a visible teaser before purchase, then all the text after purchase.

My question : how to selling per-node access without creating two entities ?
It really depends on how you want to display the content to your customers. For example, you could show a teaser of the content page via Views. Access to the full content page could be contingent on node access implemented via the Content Access module. You then just have to figure out how to display to the customer which articles they have full access to - for example, a "Purchased articles" View that shows all fully accessible articles using a node access filter.