Lots of questions but here is a short answer. The RV6 was good in its time and is a good value today, if you're careful not to buy junk and willing to do some restoring. I wouldn't worry about vintage, because basically it was the same scope with minor changes over the years. The optics typically were very good to superior.
Plan on recoating and decide before you buy if you can afford this. The original scope was not perfect but a bargain in its day. The mount is just adequate and the drive while functional has lots of slop in the drive train.
Good luck on your venture.
Cheers, Bill