They're very common — to the point that I wouldn't bother to check in advance. I'd just assume they're likely and plan to run the built-in pixel mapping function if I notice any.
A lit-up hot pixel can be distracting and annoying, but once mapped out, the impact is something less than a 0.0001% loss of resolution. If I'm buying a camera that doesn't have pixel mapping as a user-accessible feature, I make sure I've planned for the possibility of a couple of weeks turn-around from a repair center.
(I know Olympus and Pentax cameras have the feature; not sure of any others. There's a common belief that Canon cameras do it when cleaning the sensor, but this has been debunked as a myth.)