I like keeping everything in house. Get a few shirts to try out if it will sell or not, that way you are not out a bunch of cash. Make sure you use a printer that has experience with keeping a soft hand on the print. Ask for samples before committing. If you can find someone that is willing to have you supply the shirts, you can save a bit that way. I know most printers will not print on customer supplied shirts, but some do.
As for a shirt line, check out the ATC8000 from Sanmar. Combed cotton, really nice feel to the shirt. Or the Bella line is also really nice, the ATC is cheaper in price and I find the quality very close to the Bella.
As for a shirt line, check out the ATC8000 from Sanmar. Combed cotton, really nice feel to the shirt. Or the Bella line is also really nice, the ATC is cheaper in price and I find the quality very close to the Bella.