x3 on the rust. Where do you live? And check for oil leaks. I looked for a yj when I bought my tj and they were all either rusted out junk or the owner wanted the same price as a tj. What do you want to do with it? Carb models are fine for the street but if you plan to go offroad I would look for something fuel injected, carbs can get a little funky when your sideways on rocks. Above 100k is fine IF it has been taken care of, which is sometimes hard to judge. Engines that should go 300k miles can easily be destroyed in 50k if they arent maintained. If its all stock thats a good indicator that it hasnt been completely abused. Ask if it has ever been lifted/wheeled. Look underneath for signs of off road use. Step back and look at it in the sun to make sure the body panels all look the same shade of color to see if anythings been replaced.
The very best thing to do is to just ask as many questions as you possibly can. If it seems like something good, tell the seller you have the money ready but want to get a mechanic to look at it first. Most sellers with nothing to hide will be ok with that.