Once this project has been finalized and we have crossed discussions, there would be 2 or 3 Milestones set. Please do note that payment for each milestones is much preferred.
For the 1st milestone I'd show a basic design of the object and revisions can be made. After the design is finalized, for the 2nd milestone the color codes and textures would be added and you can provide the details and if revisions are possible, it can be done. Then once the design and textures are finalized, I'd make a studio render of the object and send the rendered image. If package allows it, I'd send the source file as well.