I see that this is your first post, so welcome! We're glad to have you here.
Head gasket problems were at their highest during that time period, dropping significantly in the next generation. Though if a Forester has made it that long, then it probably possesses some extra special resilience and might be good forever.
Maintenance history is essential, especially that which involves the timing belt. If you can't get that, then be prepared to immediately get the whole timing belt job done. Not just the belt, but everything that touches it.