Assuming you have a solid professional and personal network you can ask people if they would be happy to pay a fee for successful introductions. Some companies already have re-seller or affiliate programmes in place which you might be able to get involved with.
For example if you refer someone to a Mortgage Broker to save them money on their mortgage the broker may share a small portion of their fee with you if that deal goes through. You've added value to the person you referred, who saves money on their mortgage, and given the broker a new client so it's a win-win situation.
This can work over many industries - all you need to do is understand more about their business and what kind of clients your network is looking for - and then provide professional, qualified introductions.
I have no issues paying people who bring me solid business - I wouldn't have had it without them and paying them encourages them to bring me more!