Go to the Glossary of PPC Characters. There are directions for all kinds of material for your characters. There are bit characters with only one appearance that are linked. There are characters that have a homepage, but no spin-off yet.

You don't have to link to your spin-off, but if you have other material posted online (and you have Permission) you can post a link to 'home' instead of 'spin off' while your characters are being written.

You don't have to redlink. Just be sure to change the link to the actual spin offs when you do manage to make a spin off for them.

Don't worry guys-- we (and by we, I mean the amazing Neshomeh) already thought of this stuff! Just read the directions and it will serve all of your character-linking needs.