Fake Money Used to Purchase Classic Car

If I got paid in fake bills on a car, I'd shut F up, and spend it discretely here n' there until it was gone. It's no more fake than the government money, it's just that nobody really thinks about it.
What are you going to do with 'real' money'? Tell the government that you want to exchange it for gold or silver?

$18,500 worth of counterfeit $100 bills equals a potential 185 felony counts if it's all spent "discretely here 'n there until it was all gone".

Good luck with that.