To be blunt, I feel quite strongly that this is a bad idea. You might find business in this service, but only in companies which don't know any better. And if you can sell a service like this to that type of company, everyone (you, your client, their candidates) would be far better off if instead you sold them consulting services which made them more competent. Give a man; teach a man... right? To explain: Remember,…
Companies already do that through external recruiters. Just that they are not technical hence you do not get any tech questions from them. They only do filtering by grepping for technologies and experience in your resume. I would do a little bit more than that. Go into tech questions. I don't think it's very much different than that.
Correct me if I am missing something. Sorry it's a 3 day old thread but somehow every time I think about any downsides for the candidate I am still trying to find one really good one. It's not that I am trying to run this idea and hence I am biased. I am thinking in unbiased terms if you believe me.