I need to hire a commission-only Business Development Manger to drum up new opportunities for my startup technical staffing firm.  I'm offering up to 50% commission of generated revenue, if they also source the successful candidate.  Otherwise, it's 25%.  Is this realistic?  I'm open to any suggestions or advice anyone is willing to share.

(FYI, in the future, once my company is generating a little income, so that I can afford base salaries and other perks, I do plan to make these options available to my salaried staff.)