Can I B-line vessel of hatred to unlock the mercenaries for my account?

So my wife and I just picked up the game and are loving it.

HOWEVER

I want to play solo with a separate character. But I want to have the NPC’s with me so I’m not literally alone.

How much of vessel of hatred to I have to complete to unlock the mercenary hideout for my account?

That way I can start my solo run with access to them for the base game. Is that how it works?

My idea was to make characters that start on that campaign state and we could just rush it together not paying attention just to get the unlock. But how long does that take realistically? All the “game guides” provide no answers.

I really wish they just had these NPC’s in the base game man, I hate blizzard sometimes.