I have experience with Yahoo! Search Marketing, Google Adwords, MSN AdCenter and many 2nd Tier Engines. I'd like to start consulting but don't know where to begin. What do I charge for my services?
There are many companies/web businesses offering PPC consultancy and support. Search engine optimization companies often include this service. I suggest you check out their websites and study their offerings.
Bruceclay.com http://www.bruceclay.com/web_ppctoolset.htm charges $14 per keyword per month (even if your spend is thousands of dollars) with a $1750 per month minimum.
Portent Interactive http://www.portentinteractive.com/services_ppc.htm charges a fixed monthly PPC management fee, on a sliding scale based on the amount you're spending on click charges. So if you spend $500-1000/month, for example, you'd pay Portent $500/month.
Other firms charge a percentage based on total click charges. That means you pay for clicks whether they bring you business or not – and anyone can generate traffic.
As for getting customers, then I suppose one way would be to use what you say as your extensive knowledge in PPC in getting customers for your business.