Hello,
You can create a free product which will give 14 days of subscription.
Thanks to the HikaShop product limit system, you can allow a user to just buy that product once.
Afterwards, you can have renewal (paid) products in order to extend the subscription with a monthly recurring or else.
The customer will see in its subscription panel that he can renew its (free) subscription.
Regards,
Jerome - Obsidev.com
HikaMarket & HikaSerial developer / HikaShop core dev team.
Also helping the HikaShop support team when having some time or couldn't sleep.
By the way, do not send me private message, use the "contact us" form instead.