The IRS and selling personal cars???

[Zedder]

Being Canadian, I have no idea what the IRS has to do with selling personal cars, so maybe some of you can help me out. I have been trying to put a deal together on a super nice '67 Z-28. We agreed on a price yesterday and started talking about payment and the owner seemed really concerned about the IRS knowing how much he sold the car for??? What does the IRS have to do with selling a personal car? This guy is not in the business and has owned the car for years, so if he's making a profit, does the IRS really care? Thanks for any help you can provide. I like nice, simple car deals and this one is getting a little too complicated