Reasonable Pricing Scheme for Local Business Advertising?

I am starting a new business applying internet marketing techniques(pretty much anything you can think of that might work) for local businesses, but the one thing I'm getting hung up on is my pricing scheme.

My plan is to charge a reduced monthly fee for one or two months, while basically throwing everything at the wall and seeing what sticks. After this period, I would then let the client see how well each service has done, and decide at that point which ones they want to pay for and which ones they do not. At which point they will begin paying a monthly fee for each service they want to keep, OR, alternatively, pay a single lump sum to purchase the various traffic driving sites, articles, videos, etc.

I suppose what I'm wondering here is what you Warriors think my baseline should be for the initial 'work in progress' charges, and for the lump sum.

I plan to be much more flexible with the other fees, working on more of a 'common sense' metric.

Unless the general consensus is that the entire system I'm suggesting is a mess, at which case I'd like to hear some alternative payment schemes.

Thanks in advance!