Welcome aboard!
There certainly are quite a number of things to look for... and to look out for, when shopping for any used motorcycle, not just a BMW airhead. Tires, tubes, etc. are indeed pretty much assumed to be in need of replacement unless you buy a bike that someone is actively riding (and even then....)
some models have certain peculiarities that others don't, so it might be best to just keep shopping and learning, and when you see a particular one that turns your head - post us a pic and the details here and we can help you based on what info is available.
There are also, for example, instances of seller ignorance - or willful misleading? - that can inadvertently show up... for example, here is a clean looking (all bikes look nicer in pics than they do in real life) R65 for sale in new jersey. It is advertized as an LS model, which would make it rarer and potentially justify a slightly higher price... but it isn't an LS model. It is red like many of them were, but it has an aftermarket fairing, the standard R65 seat and rear tailpiece, and standard snowflake wheels from the regular model. Possibly the bike was originally an LS, and someone decided to throw out all the LS-specific parts and put standard R65 model parts on and repaint it all a non-standard paint scheme - but I doubt that. It could be a very nice bike all the same.
http://newjersey.craigslist.org/mcy/4586874641.htmlSo, just keep looking and learning, and don't be afraid to ask questions!
I see that there is a 86 monolever framed R65 for sale in the Springfield area. While it does have the larger frame of the R80/100 of the time, it isn't a bad handling bike - just not quite as quick turning and low in the seat as the twinshock models ->1985. Still, the monolever bikes are decent smooth riders, pretty forgiving, easily run tubeless and are also fairly straightforward to operate/wrench on - might be worth a closer look unless you need / want the lower seat height or shorter wheelbase.
http://dayton.craigslist.org/mcy/4603915317.htmlAnd, +1 for putting a msg on the ibmwr.org webpage like Monte suggests!
-Mike