Affiliation programme

Hi We have a website that sells advertising and we would like to offer affiliates the chance to sell on our behalf and track their sales. We don't have much experience in this field so would need a coder who fully understands what is required and may have to think for themselves without us giving the full instructions as we don't know exactly what those instructions might need to be. We don't know how this tracking works We just need to know accurately, so we can be 100% fair, who made the sale, how much it was for and how much we need to pay them. Cheers Jen