I want to start a book & music store focussing on "New Age" books & music.
Can someone tell me how I source my material, find the right
publishers & music companies. What kind of minimum investment should I
be looking at? What kind of margins should I expect?

I'm sorry you did not get an answer. I can't give any advice on the
book and music wholesalers, except be careful that you have your
agreement spelled out in detail. Lots of them will treat you well
while suppling you with $10,000 initial inventory, but poorly on your
$50 per week orders. You may be better off both long term and short
getting your books from internet retailers, and paying retail from a
local competitor for an occasional book.
 The wholesalers typically let you sell their books on consingment,
but your margin may be less than half, the potential profit if you pay
cash. It is in effect a high interest loan you should avoid if you
have enough startup money. Do learn to read the fine print in
contracts, otherwise you will surely get ripped off sooner or later,
likely both. Typical lawyers will insure no profit so avoid them
whereever possible. It is a jungle out there.   Neil