It depends on the model you are going to get. I have a 1998 Saab 900 SE Turbo Convertible with 143 k on it. Recently I fixed a sticky WasteGate lever that was causing loss of power when the turbo meter reached the orange zone.
The starter was giving a humming noise when the engine's just started. I changed the starter and the noise was gone.
Other than those two problems the car is great. With a small 900 cu. in engine its power to accelerate and reaching high speed is just unimaginable. If properly maintained these cars last forever.
Use synthetic engine oil and change it every 4000 miles. Also, use a little high-octane gas (89 - 90) though it can adjust to any grade by manipulating the knocking (the lower the grade the higher the knocking).
Good luck!