If it looks OK, runs well, and has a new cat then the main things it could fail on are rot, brakes, bushes, suspension, steering. Any of these alone are not too expensive to fix, but if you have 3-4 items the bills add up!

Some cars cost more than others to run ... I just found new front discs and pads for my Mercedes are over £500 at a local Merc independent. Sigh.