Players on Shared Campaign

does the player have to pay and have a subscription too?

so if i get to join a said DM then i can play in the DM's campaign without having to buy a Beyond Subscription?

It doesn’t even have to be the DM, I believe. As long as someone has a master-tier subscription, everyone can share everything. 

do you have to make a character for that campaign or can you use one you already have?

nice

I find that if I try to make a character outside of the campaign, I do not get the benefit of shared content

Quote from The_Crycket >>

I find that if I try to make a character outside of the campaign, I do not get the benefit of shared content

 Yes, that's how it works. Content is only shared within the specific campaign.