Best used TT for under $1k?

Rob, there are huge difference between many turntables and new Technics mk7, especially at your price range. Detachable headshell and VTA on the fly are great features to have, high torque motor with immediate start/stop will serve you for next 30 years without service. With mk7 you don't have to change or upgrade anything, the build quality is outstanding (I hope you can find one in the shop), this is solid Made in Japan, heavy turntable on adjustable feet. What is great is resale value. If you can buy this turntable for $900 new with warranty then I doubt there are better option under $1k.  

VPI HW-19 look hard and you might score a mk IV for under 1K

The mk7 is not made in Japan. It is made in Malaysia. 

Rega RP-6.

How long is a piece of string?

It's ultimately an unanswerable question - far too many variables.

Assuming he hasn't yet found one:

That said, I'd suggest staying with a brand that has been around a long time continuously, has a proven record of servicing and supporting their gear, and that is reasonably widely available.  

If he wants something that's basically "turn-key," a Rega is the first that comes to mind.  Excellent reliability, excellent sound, easy to use, etc.  If he wants to noodle with it more, a used VPI could be a good choice, although there are a LOT of possible variations.