In your specific situation for RE this is how i would do it:
Get a couple of realtors together (3 or 4) from different zip codes and then get a crm with cyclic rotation so the leads rotate betweeb 3 or 4 accounts.
Then, charge them a fixed monthly price as advertisement where you guarantee them leads so its not just a crappy ad on a website but a guarantee that they are gonna get quality leads from search engines (best quality...explain why etc)
Your profits will be the difference between that monthly fixed price x 3 or x4 and the PPC costs.
And you dont have to deal with them not converting leads or with comissions becuase they GET ads/advertisement
And of course get the damn bills before starting.
You DO have to show them something beofre, the site, the CRM etc...add value before, why is this different for THEM, etc.