Where i could find a large quantity of items?

I would like to start my own business and was wondering if:
1. Where I'd be able to get a large order of iphone cases with my own design on for very cheap.
2. Where I'd be able to get a larger order of printed tee's with my own design on for very cheap.

Both i would want the best possible quality but for as cheap as there can be

Any suggestions would be highly appreciated. Thank you very much.

Added (1). I would also like the company to be very trustworthy

Get the hardwares and print it yourself keeping some employee. Tee printing is not going to require a million.