According to the manual, if the car is operated in "severe conditions", the interval is 60k miles for the timing belt. They don't specify a replacement interval for "normal" operation.
The 4AGE engine is non-interference, assuming you have stock cams and valves, and the head and deck have not been machined down. So if you break a timing belt, you get stuck, but don't destroy your engine.
If you don't have evidence that a quality timing belt replacement was done, I would replace it as soon as I bought the car.
And yes, it is an excellent idea to replace the water pump and the timing belt tensioner at the same time with QUALITY parts. Not ebay junk.