Cost Per Sale

I am at present running a Forum posting service. I have a blog which speaks about the service and the direct link for ordering the service. I would like you to generate sales for my service. I am looking for 40 sales in 15 days. The days will be calculated form the project commencement day. You can find my blog and direct link in the file attached. Since this is a Pay per Sale kind of project, i cannot provide upfront without any sales. Maximum i can do is, if you finish half the no of sales, then i will release 50% of the total payment. Show me the sales, get paid ! Please make sure that you have enough links or proofs to show that the sales where from your side. Thankyou.