First you need know what the total amount of the payback will be. As said in another post you should be looking at something less than 20K on a 1998.
Based on my experience purchasing 3 used units in the last 10 years, plan on spending 3-4k on new tires and a few repairs that will be most likely needed. I knew this going in on each unit and bought them at a price that reflected those conditions.
Do a very good search for any water damage/stains that may be present. Look in every closet, drawers, around showers and tubs, under the sinks and along the inside headliner and vents.
Hope this helps.
Michael