How to get the Duke O' Death?

I was watching some videos on YouTube showing how to get the Duke O' Death in GTA 5, however what I have seen is sort of unclear.

Some people say you must be a returning player on GTA 5 to get it (what does this mean too BTW?), some people don't say that. Some people say you have to be Trevor, some people don't. Some say the time of day matters, some don't. And apparently you can buy it from Warstock website (I can't).

Can someone please tell me how to get it?! GTA 5 came with my PS4 (I didn't play it on PS3) if that helps.

I answered a similar question recently. It is one of a few returning player exclusives. That means you have started playing on the previous generation (Xbox 360, PS3) and moved over to the current generation (Xbox one, PS4). There is no other way to unlock the Duke o Death. Guides that tell you how to unlock it, but don't mention "returning player reward" quite likely assume you have got the content already, and therefore must already be a returning player.

What I can not confirm is whether you can bring the content in if you start the game on a new console and then play it on an older console.