Set up an offer for t-shirt sale

I need someone who can set up an offer for me. I am going to sell a special type of t-shirt. So I am going to offer the customer a product with price. I have the design of the t-shirt ready. Price for buying one t-shirt is 10usd. Then whoever buy the t-shirt can sell it for the price they want. I have a customer who is willing to buy 500 tshirts of this product. But i need to set up an offer. I need somebody professional that have done this before. I offer you 10 usd for this job.