Good news: you won't have to pay to access the Samus and Link costumes in Dynasty Warriors VS.
Bad news: you will have to play the game's tutorial mode.
The collaborative Zelda and Metroid costumes, officially known as "Link's Clothes" and "Zero Suit," were added to the VS official site today. According to the site, you'll be able to unlock the outfits once you've advanced in the game's tutorial mode.
The costumes can be used to dress your custom general in the game's My General character creation mode. For a look at some of the other options, see this page at the site.
Link and Samus aren't the only "Nintendo characters" to appear in the game. Your Mii will also appear in a support role, handing you helpful items during battle when you're in a pinch.