If there is any blue smoke when you start it up the turbo is probably on its way out, walk away.
If the car has warm when you get there I.E its been started and run already, I'd be suspicious. They tend to just smoke on a cold start
Turbo is about 650..
The Light Pressure turbos were much more fragile than the full pressure/high output ones so its worth finding out which one it is.
Don't know if you can find out the history of it, if its been a motorway car than its had a much easier life than a taxi..!
If there is a good specialist near you, thats a help.
Remember Saab are now bankrupt, spares shouldn't be a problem though, its mostly GM bits
My 9-5 estate needed a turbo, but that was the only big thing in 6 or so years of ownership.
I got 25mpg round town 32-35 on M'way but its a much bigger car than the 9-3.
If its in good nick why not? I still reckon Saabs are quite an unusual choice, I liked mine!