Good tips. (You should see the amount of wear I have around the crank on one of mine -- though it seems to work fine.) The only problem is getting a photo in an eBay listing that shows this area with enough clarity.
A follow up tip is read the advert properly. Has the camera had professional use, has it been regularly serviced, does it show the signs Dan's highlighting. Any of those should be warning signs, and good reason to be careful not to pay too much for a well used Rollei TLR.