What are the requirements for the Greed portal to appear? [duplicate]

Solution 1:

There isn't much known about the portal and the conditions under which it spawns. This article covers some information about Greed's Domain.

According to the article you'll need to be at least level 70 and in adventure mode for it to spawn. Also it won't spawn in (Greater) Nephalem Rifts but it can spawn in Whimsydale. Another thing to note: There is no way of increasing the likeliness of spawning one. Apparently it's completely random.

Now from personal experience: I've only been there once and while I wouldn't consider myself a hardcore diablo gamer I've killed about 150 Goblins since Patch 2.1.

So basically the only way to "Farm" these portals is farming treasure goblins.

Although the wiki states that most player get a Portal every 15-20 goblins, I'm personally really skeptical about the numbers, since I've only entered a portal once after 150 but maybe I'm just unlucky.

Solution 2:

The portal to The Vault will not spawn inside a Nephalem Rift (and Treasure Goblins don't spawn inside of Greater Rifts at all) and only players present in the game when the rift spawned can enter it.
Greed portals can only spawn in Level 70 Adventure mode on any difficulty.

Source 1 and 2