Yeah, I've heard of things being outsourced too.. There is a lot of GMO/sprayed cotton in India though.. (thanks to Monsanto..) better be careful..
If this would be a green and ethical line of clothing... In that case, maybe the market would be interested.. Also depending where you want to sell, the pricing & the competition.. A lot of big retailers and 'big names' in clothing have done badly, still people may be interested in truly 'green' products..
(It's not so easy to make 'truly green' though.. I looked a bit..

of course there can be good approximations..)
Anyway, wishing you luck with this.. Sometimes I dreamed about having my own (very niche) line of clothing too..
Oh, and not sure if you're looking for info on branding or also on creating the actual green & ethical clothing? There is a lot of info in books, and some colleges/universities may have courses about making the industry greener etc. (so even if you don't go study, you could get materials, books, notes from lectures etc from any students..?) Or you could get consultants etc?
Of course it is also great to learn from people who have already done it, and are doing it successfully.. Go check out their websites, read interviews or books about them.. visit shops..
A real live mentor (or a few) would be ideal, you can get a lot from just reading about what other people did & are doing too..