Top 10 in Google , Yahoo , Msn ......... searc

I have a website same as freelancer.com, which acts as an intermediary between the freelancer and employer. I want top 10 in google, yahoo, msn... The words chosen will be those that are more profitable for my website. In your budget you'll have me say the words with which we will work. 1) No black hat techniques. 2) I only Pay when service is complete and rankings are there. Money will be put in escrow. 3) I only pay the bid price no other. 4) If dont there are result expected each month will not be paid I am on a budget. The bid price is an ongoing monthly amount that will be put in escrow and released after the month.