I have had a 1996 900SE with the turbo-charged four-cylinder engine for three years. I strongly concur in your plan to take the car to a Saab specialist for a check before you buy it.
In test driving the car, I would: (1) find a rough road to drive it over to check for rattles, particularly from the front suspension; (2) check that the heated seats are working, since they are very expensive to fix (about $1,000 in the U.S.) if they're not; (3) be sure that you can find a seating position that's suitable for you, since (at least in the `96) there is telescopic steering, but not tilt wheel; (4) make sure that there is enough adjustment in the driver's side mirror, since on some 900s the mirror doesn't adjust far enough out with flat glass that is required in the U.S., and presumably in Canada (as distinct from the convex glass that is standard in Europe).
My understanding is that the four-cylinder engine has a timing chain, but the six-cylinder engine has a timing belt. As to maintenance costs, I have found them to be much higher than on other cars I have owned. In particular, the parts seem to be many times higher than those for other cars.