What reward are you using for a SaaS referral?

I am setting a signup goal, not a visit goal. A visit is too easy to inflate, and the reward should fire when someone actually creates an account. Curious what others are offering: account credit, a free month, or cash after the referred person stays. For a $9/mo tool, a free month for both sides feels clearer than a small cash payout. How many signups are you requiring before the reward is earned?