A lot of people save up to own cars like these. Then realise they can't afford to put fuel in it, they can't afford to insure it etc so they sell it on. Some of these cars are 23 years old so is 15 really that surprising. I once had an e36 with 18 previous owners the car had been drifted and generally had a very hard life but it still drove well and looked good. Supras/Soarers etc are seriously well made and can survive a little neglect that's just part of the fun of owning older imports is fixing all that stuff up putting other peoples wrongs right.
BUT if the owner before you was a lunatic then your going to have your work cut out