You can download the 14 day free trial right away. The game does have a subscription model, entry packages start at £7.69 per month. FFXIV is gorgeous, looks great on the PS4, gameplay is smooth. No voicechat, can plug in a USB keyboard to communicate with other users.
If you do like the game and want to continue playing, you can still purchase the PS3 copy for under £5, comes with a 30 day free trial, upgradeable to PS4 version for free.