Knock sensor and brake replacement?

I'm looking into buying a car from a coworker she has a 2003 ford explorer. She says the only issues are the knock sensor and the brakes, is it worth it to buy the car and replace these parts? Can anyone give me an estimate on how much it could cost for parts and labor? Please and thanks

Ford Explorers have brake issues.
2003 fords were of low quality.
I wouldn't touch a Ford of any type. Or gm

Get a mechanic to look at the car. It might need a new engine.
When buying a vehicle, do not trust anybody except your dog.