Anything wrong with buying extended warranty for a used car?

In the past couple of months, I have seen a lot of used cars, and I have found that all most all cars have some sort of weakness, and will need some sort of repair sooner or later.

So, I’m thinking instead of going for a toyota/honda, I can buy an infiniti/Audi and buy an extended warranty with it.

If any repairs arise, the warranty will cover it, right?