Twitch Prime gives you a number of benefits in GTA Online, including:
-A free property in the game
-Twitch Prime status, which gives you access to exclusive vehicles, clothing, and other items
-A discount on in-game purchases
To get Twitch Prime, you need to have an Amazon Prime account. You can sign up for a free trial of Amazon Prime here. Once you have an Amazon Prime account, you can link it to your Twitch account here.