Actually I should clarify that right now, the module is going to work off of roles. So, not everyone can create the custom product node, only members of the special user role. It would take a little bit of refactoring to make it so that a user has to pay before they can make the content. It's more like "I have permission to create a product, which can then be sold." I think what you want is "I need to buy the node that I'm creating before it is sold."

That's probably better suited for the module that JuliaKM is creating - pay per node, or uc_nodetype. I'll have to think about it more to figure out what those changes to the workflow would entail.

Let me know what you think.