Welcome.
You can't really go wrong with a R65 as your first motorcycle, it you get one that is sound. My first motorcyle was an R65 (I still have it) and it was my only motorcycle for over 30 years!
IIRC, the dual shock R65 are the "smaller" ones. I think that when they went to the single shock version, they used a larger frame like on the R80. Others can correct me if I am wrong. The smaller frame ones are reputedly the more nimble of the two versions.
Duel Brembo - I believe that in 1982, they went to the single ATE (other than on the LS version). The singe ATE works for me.
As for individual condition items, I am sure someone here has list of what to check out before you buy. From my own experience, check the fuel tank for any signs of leakage or rust (particularly on the bottom seam area, or particles inside the tank). If they have not been properly stored for the winter, there is a good chance that they could be rusting through by now, and it is not cheap to replace and repaint (if necessary). Also, check the steering head bearings for notchiness - they tend to go every 30,000 - to 40,000 miles and can be a significant repair job.
I wish you well in your shopping and selection.
k_enn