Thorin & Co, Gandalf

Does anyone have any answers or maybe guesses to where Thorin & Company were living before their quest to Erebor? The Mountain was occupied, they weren't with Dain in the Iron Hills, not Moria, what other Dwarven Homes are there? Does it say? How and why did Gandalf ever get involved anyway?

I believe they were living in the Blue Mountains. As for why Gandalf got involved, if you have Unfinished Tales (or can get hold of a copy), read the section entitled "The Quest of Erebor".

There is also a brief account of the meeting of Gandalf and Thorin in Appendix A of 'LotR', in the section entitled "Durin's Folk".

Sorry, I cannot remember the exact source, but I believe it was one of the appendices of LOTR. The source states that Thorin and his company were living in Ered Luin, with the remnents of the people of Nogrod and Belegost, as well as those dwarves of Durin's folk who did not move to the Iron Hills after Smaug plundered Erebor.

As to how Gandalf got involved....

Well, the whole thing was Gandalf's idea . The White Council saw the gathering of Sauron's strength even then, and Gandalf was worried that the dragon's presence would be used to Sauron's advantage in the up-comming struggle. It is almost as if, although he planted the idea of a treasure recovery in Thorin's head, he in fact was hoping from the beginning that the quest would end with one dead dragon.

But hey, what else could you expect from the wisest of the Maia?