Is it Legal to Earn a Commission on an Assignment Fee?

[Joe Kamenar]

I am working on a website that lets investors who have a purchase agreement assign that agreement to an end-buyer, in exchange for an assignment fee. I know that a non-Realtor can't charge a commission on a sale, but can said person charge a percentage on the assignment fee, for example, having the potential end buyer put up 10% of the assignment fee into an escrow account, and then if the deal goes through, the company gets to keep that escrow amount.

All views on this would be appreciated.