Good luck with the wheel build Jags
I am so glad that you are getting a new SON hub, as a wheelbuilder of some experience I would never offer to use a 2nd hand hub unless it was retro/old/had been examined at bearing races and spoke holes for wear with a magnifier by me! and then fitted with new races, ball bearings and cones adjusted. With a SON hub you simply cannot do this and have no way of knowing what you are buying (customer) and no way of knowing what you are selling (builder). On a personal note my SON was rebuilt in Germany via SJS last July, it was 5 and a bit years old, just out of warranty, but done through :)excellent SJS service as always, it was the magnets that were sticky.
On your spokes, I hope he is using 14 gauge spokes and not 14gram ones!
safe cycling
Dave
www.davesbikeshed.co.uk