Can I exit the house with the radon pipe just above the foundation?

Radon vents are power since Radon is heavy. The problem with a vent so close to the ground is that the heavier air/radon mix will fall back to ground level and possibly seep back into the house. You could vent out at the foundation with the vent motor in the basement but then run the vent outside to the roof . Most people don't like to do this either since the piping is now under pressure and will leak if not properly sealed. Usually the vent motor is in the attic and the ducting is snaked up an existing chase or through a closet.