Need a contingency agreement to get paid anything significant. Doesn't make much sense since a good referral is worth a lot no matter what source it comes from.
Right now I find out as much as I can about a company and if I like them I try to get an agreement. If I can't and a candidate seems like a perfect match I'll still refer them just bc I'm trying to build out relationships with the hopes of getting an agreement for the next one.
As I build out my sourcing tools I'm using and automating more of my business I will either sell my tools, get agreements with everyone, experiment with all alternative payment methods (retained agreements, SaaS model, etc), or all of the above.
I like the outlook in the industry though. Lots of players but lots of room for growth esp. b/c looking at eng- lots of future demand for jobs, lots of companies moving between stages (startup to big co), and lots of companies bad at retaining employees.