[The_DaveG]

I've negotiated deals like this in the past and white labeling products are a great way to go about it.

In the past I've done an $X upfront as the cost to create the white labeled product and then some % of the revenue based on the value that you bring and the time/cost it takes you to do so.

Best suggestion is to think of the numbers that would make you insanely happy, double that, and then use that as your starting point for negotiation.