Commission
A percentage of each job. It scales with job value, so a large panel or engine job costs you more for the same introduction, and some platforms take payment through their own system.
Pay per lead
A fee for every lead, whether you win it or not. It works when leads are tightly matched; it hurts when they are not your kind of job or are sent to many businesses.
Flat monthly fee
One subscription for every matched job in your categories and regions. Your cost per job falls as you win more, and you keep the full value of the work.
Questions to ask any platform
How many businesses see each lead? Can I choose my services and regions? Who owns the customer relationship? Is there a contract? Can I try it before paying?