Re buying a used bike: IMO, you can't trust anybody selling a used anything. I bought my Norton in '06 from a very well known US seller of Brittbikes who stated it was ready to ride across the country! Not being able to go pick it up, I had it delivered via truck and it took me a full day to get it to fire at all and it ran terribly when finally started. The fix to get it running was to replace the bad Boyer (I switched back to OEM points/AAU). Also: it had
no oil in either of the internally rusted forks, it had one broken rear shock (rod separated internally from the plunger), and a clutch so stiff it nearly took two hands on the lever to release. There was more but that will give you an idea. The bike was essentially a non runner and UNSAFE to ride. ASSUMING they could have gotten it started, there is no way it could have been ridden safely around the block let alone across the country.
Due diligence is mandatory for such purchases and I definitely failed on that account because I trusted the well-known seller.