All depends on what you're doing.
There's tons, but most will only deal with high quality buyer leads in certain niches. Most will also only want to deal with people that have xxx leads a week, and they will pitch them complimenting offers to your front end, and you'll keep up to 40%.
There's ton's of scenario's and ways to get jacked this way too though. If you have a bunch of data (profiled buyers/prospects) and are looking to hire per call or batch of calls, you'll probably pay out the arse and there won't be incentive on their behalf to convert.
If you still come up short after the responses here, feel free to reach out and I'll try to point you to a few people that may be able to help.