Sounds like he'll throw in some extras, which could be good. What exactly are they?

How much for the extra wheels?

He sounds okay, and like he knows a bit about bikes, and is conscientious.

I would want to find out more, though.

The fact that he has replaced that cable suggests a fair amount of riding.

I would have to wonder what kind of shape the bearings are in. And can you overhaul them yourself if necessary, or are you willing to learn?

They may or may not need replacing before who knows (without further information) how long.