I'm pretty sure that's not a factory color, like 1jeeplvr said check for rust everywhere. With a body repaint, the prevous owner could have easily sprayed over the corrosion on the frame. Also 18 mpg highway for a 98 auto is pretty optimistic. I would pass and look for something that is more towards stock.
Check the frame, look for dark spots around the engine or dirty spots, dirt tends to cling to leaky areas. start her up, listen for ticks in exhaust and the head. If there's no rust and she sounds fine, I wouldn't have an issue w purchasing the jeep. They are very easy to work on and diagnosing issues is a breeze on a 98.
If there is an exhaust tick, have them fix it, then purchase.
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