Hi Folobo
DPS Classic is supported for the forseeable I'm told...
BUT: You are much better off recommending to your client to go with DPS2015 as the development roadmap is pretty exciting and you'll get better support if you're part of it.
In DPS2015, you can publish individual articles, and 'collections' of articles. And you'll need relevant product IDs registered with Apple / Google for anything you wish to 'sell' (via collections only). Including any subscription offers.
I don't think its possible to sell 'one article' unless its part of a collection (issue) or part of a subscription. I suppose you could make a collection of ONE article and sell that...