We have never hired a marketing/sales rep but we have 'rewarded' people for referrals. What we did was offer $50 for an appt and a $50 bonus if the provider signed. Then we would give them residual compensation for the first six months we billed for the provider based on the amount we charged. So for example, they set us up with an appt, the provider signs, and agrees to pay a $1000 flat fee per month. The person would get:
$50 appt bonus
$50 sign up bonus
$100 1st 3 months ($300)
$50 months 4-6 ($150)
The residual bonuses were paid each month so they would receive $100 first, then $100 after the provider paid month 1, $100 after the provider paid month 2 and so on. For a total bonus of $550 over a 6 month period. Sounds complicated but it worked well for us. We would get a year (minimum) contract so we were guarenteed $12000 for the $550 commission. For us, $550 is worth paying for an account like that. And usually we would end up working for the provider for longer than one year, so the commission was definitely worth it. And the commission is based on the size of the accout so you don't pay big bucks for a part time social worker.
Hope that helps!