After examining the bike and finding it to be in even better condition than I expected, I decided to take it. The rear tire tube was indeed leaky, and the tire itself was nearly new, though covered in that green SLiME grease stuff. Also, one spoke had come off of the rim. At $75, I thought it was worth the risk and will be heading to the LBS tomorrow to find out how much it will cost to fix that one spoke (and hopefully not have to replace the entire rim).