Ask HN: What does a good referral agreement look like in SaaS?

I am doing research on what a good referral deal looks like in SaaS. The goal is maximize the number of partnerships with aligned products, and eventually find a strategic acquirer.

I have one conversation that was initiated by a complimentary SaaS and they are asking for me to provide the terms. I am considering offering 20% of the first year revenue generated by the client, paid out after every month that completes.

What's a good benchmark to evaluate whether this is a good offer?