What is the cost to join a TM Network? Is it just that you have to have a Resonance Link to the Network? On a side note, is Resonance Link dedicated to a single entity when you choose it or can you change the subject of your Resonance Link? If so, what is involved in the change?

Graywulfe

I'd say, it's the same as finding an initiatory group or any other group contact.
In our games, in includes a bit of roleplaying, a bit of running the shadows, a bit of Karma, and some favors called (or maybe payed for).

Anybody else have a RAW/RAI opinion on this?

If the GM allows for Group Contacts (outlined in RC), you could start with one of the established TM Networks listed in Unwired as one of your contacts, or work one out on your own (with GM's approval), all totaling the usual BP/Karma cost to start with the group. I don't think the Resonance Link echo is required in any way, but the benefits of it shouldn't be brushed off, especially the broader application allowed for a network instead.

Unwired, page 144, does have something set for finding a temporary party network, and depending on RP it could turn some of the regulars into an established network with the character.

As far as the Resonance Link echo, the way I read it makes it sound like you establish the link with one technomancer and that does not change. Personally I'd rather reserve this for a Network instead.