I am a long time web developer, but just recently I've had two or three clients interested in marketing their sites using Cost-Per-Click advertising (Google Adwords and Overture). I've worked with CPC before, and I think this could be an additional way for me to generate monthly cash flow, so I am interested in getting involved with this.... but I don't really know how to charge for this type of service.

Do any of you offer this service to your clients? What is your typical markup for managing this type of thing... from my small bit of research, it seems that most firms are using a flat-fee per month approach, rather than an hourly charge approach. I think this would be easier to keep thing consistent.

Example... If a client wants to spend $1000 for a CPC campaign on Google. What % should I charge for the management services. My initial thought is somewhere around 30-50%, meaning $600 would be used to actually buy up the keywords, and $400 would be the management fee (profit). Please advise.

Bayzing