Best bet is to contact a local contract printer, and show them your idea. Run a small batch of shirts, don't focus specifically on profitability but on building a market. Once you get that market, you can run larger batches and make profits.
A forum community dedicated to T-shirt merchants, professionals and enthusiasts. Come join the discussion about graphics, commerce, dyes, prints, collections, guides, displays, styles, scales, equipment, accessories, reviews, classifieds, and more!