CAC for a business paying trailing commissions
So I am looking at SaaS business model. They are paying re-sellers a trailing commission of the clients that they sign-up/sell to. It's 10% annually of whatever revenue their client pays. There are no upfront costs to the company.
How would you calculate the cost of customer acquisition? Someone said that I should take the commission paid over the estimate life of the customer and add it up. But that doesn't make sense, because the company has no upfront cost.
How would you handle this situation? What would you calculate the CAC to be?