Its not a hard job to do, if you end up buying this car either find a good independent shop or plan on doing the majority of the routine work (and this is routine) yourself or it will cost ya.

You dont say what the mileage is, even if it is less than 70k, I would change out the timing and serpentine belts. I might even go so far as to do the water pump since it is pretty much out in the open once you get the timing belt off. Go to fcpgroton.com for the best deals on parts for this car.

If there are no maintenance records then it sounds like there wasnt much maintenance done on the car. If you can have it looked over by a good independent volvo mechanic (not by a dealer) that will help to pinpoint any problems the car might have. These are very nice cars, but they do have their issues and you should know what you are getting into. Search back on this and the 900 forums and you will get a flavor of what is involved.
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97 S90 with 176K miles still going strong