[blueunicorn6]

That would imply that he was hauling numerous weapons into lots of different hotels.

That increases the chance of him getting caught.

They might exchange the cash in a motel, but they would examine the guns in a spot where they could be fired.

Dirty dealings are done by dirty people who don’t trust each other.

[Oldeconomybuyer]

“What we know is Stephen Paddock is a man who spent decades acquiring weapons and ammo and living a secret life, much of which will never be fully understood,” the [Las Vegas] sheriff said.

My contention is Paddock has not only been "acquiring" weapons and ammo for decades, he's also been selling them illegally. That should make him a trusted supplier, no live fire tests required. Just a theory ...