[Mr.ac]

Well, that's always the downside on used wheels. It's really up to the seller how honest of a person they are, and why they are selling their wheels.

Besides what you said there is not much you can check in a garage. The only other thing you can check is to feel for any dip/bumps on the inside of the wheels.

Personally I would take them to a tire shop and have them checked for leaks and rebalance.
As for tires, eh they can be easily replaced.

Good luck.