noahwangerin, thanks for your insight. I 100% agree with what you say and most of your points were my main considerations. So, what i did in the end. I gave 2 options. The first one with a flat-fee and then another one with a kind of lower flat-fee and a % of royalties. In my mind i had this 2nd version as a kind of “discount” quote (if i get no royalties) with the potential though to become an even more profitable collaboration should the products sell well.
I do not think i would ever go for a 100% royalties agreement with no down-payment.
As you very correctly said, i hired a lawyer to compose a royalties agreement on top of the flat-fee agreement i already had.