I am currently building a financial website that is related to the stock market. I would like to incorporate an ad service to generate revenue. I am leaning towards valueclick as of right now. I'm wondering when the best time to signup for this type of service is. I understand that I have to be accepted. The sooner the better so I can have the programmer insert the code. Do these type of services require that you are up and running for awhile before you can start displaying ads?

Also, what is the best company out there for displaying picture ads?