As of April 2016:
Unlike Magento 1 (which had Recurring Profiles), Magento 2 does not include any kind of subscription or recurring payment functionality out of box. This may change in the future, but at the moment your only option is a custom or third-party solution.
Creating one yourself would be fairly complicated. You need the ability to mark products as subscriptions, to communicate that to the customer, to generate new orders when the subscriptions come due, and to actually collect payment on those orders. You will not be able to do that with any built-in payment methods. All told, it requires a lot of time and pretty extensive knowledge of Magento 2's internals.
As for third-party solutions, your options are limited since Magento 2 is still only a few months old. One is ParadoxLabs' Adaptive Subscriptions extension. Full disclosure: I wrote it.
There are no others listed on the official Magento 2 extensions page at this time.