I am not a lawyer or an attorney and this is not "professional advice."

Hire an accountant who is familiar with licensing.

Stay away from the franchising route if you can: it's expensive, the lawyers are expensive, and you are open to attack from inside and out (franchisees and customers). I was a senior executive at an Inc. Top 1000 franchise firm and saw this from the inside--though we didn't have an issue with our franchisees, I saw plenty of franchisors who did.

Learn about licensing. Figure out how to write the contract so you have control over some measurable variables, eg. customer count, revenues, # of complaints, etc. As long as the licensee remains in tolerance, they're fine, but if they go outside you drop them.

You are going to have to invest in an attorney to create the boilerplate contract, and an accountant to manage the process (which you should probably do first.) Don't cheap out. You're protecting yourself here.

BTW looks like Jeff Retchman in this thread could help you as well: https://clarity.fm/questions/1258/how-to-license-with-a-revenue-based-model