Wow, I feel like some of the earlier response is a bit overkill, but maybe that's because I only have mild-to-moderate, not strong, cat allergy. Since you say the house looks well-maintained, I would probably just have the whole home professionally cleaned before moving in -- yes, this is standard, but I would make sure the cleaners know to do an extra thorough job because of the allergy issue. Then, I would be sure to change the air filter in the home a bit more frequently than "normal" in the months after you first move in, and use a higher rated filter, so that it can continue to capture the leftover pet dander. Also, just because a cat once lived there does not mean that the cat ever peed on the floor. I've had my cats for over 8 years, and they've never had a bathroom accident. But yeah, if you find a cat pee smell or stain, then that spot will require extra cleaning attention.