My advice: You need to clearly spell out the value you bring to the candidate. If you're going to ask for payment, what would I, as an applicant looking for a job, get from you that I can't do myself? Or I can't pay someone overseas $4/hr to do for me (submit a lot of applications)? What's your specific value proposition?

Saving time submitting applications for applicants has some value perhaps, but the goal is to get a job, or at least an interview, and that's probably only incidentally correlated to number of applications submitted.

I think there are opportunities in the coaching and resume/cover letter tailoring niches. You can find plenty of people offering that but they mainly come from an HR background, not a tech background (probably because tech jobs pay much better -- those who can, do, and those who can't do, teach, in other words).

If I was looking for a job I might consider paying someone who clearly had great industry/geographic contacts, inside tracks, and advice. But then I wouldn't have to pay for that -- I would try to identify the top recruiters and get them to place me.