Very smart. CL has needed something like this for awhile. Is there a reason, aside from your small "need a coder" link, that it's being offered for free?
Yes - craigslist is free for the most part. I'd like to figure out a way to keep this as free as possible.
Maybe offer an eBook for sale (or plug one from an affiliate program) detailing ways to create effective ads with easy tips, wording suggestions, other research, etc.