You absolutely should hire a mold inspector if there are past water issues with a property. Mold cannot be painted over or eliminated by simply replacing tile and fixtures. I've had apartments that required removal of almost every wall and most of the floor to treat mold that had attached itself to studs and sub-flooring. One 2 bedroom, 1 bath apartment cost about $25k to treat, another cost about $40k (including removal and replacement of bathroom fixtures, kitchen cabinets, etc.). Both these apartments had been treated by the previous owner, but they simply washed the walls with mold-killing chemicals that never got to the source of the mold.
Mold can be found on surfaces and in the air. Make sure your mold inspector does sampling in every room, harmful molds can travel throughout the property and aren't always easy to see or smell.
Best of luck!