Why not just move this post to the buy /sell/trade section?
he's offering something of value to the community, he's a part of the community to the extent that he is a machinist with an interest in scale models and this site, and this is a one time thing - it's not like he is trying to run a sales business here. Or simply ask him to register with the site first, if you want that formality.
No need to blow this out of proportion.