After effects fade in and out expressions

Just alt click on the little clock for the opacity of the layer you want to fade on the in and out points of your layer and paste these expressions.


FADE on IN and OUT
fadeInTime = .5; // fade in time (seconds)
fadeOutTime = .5;

Math.min(linear(time,inPoint,inPoint + fadeInTime,0,100),linear(time,outPoint - fadeOutTime,outPoint,100,0))

JUST FADE ON OUT

if(time<(this_layer.out_point -0.5)){

    transform.opacity;

} else {

    ( (this_layer.out_point-time)/0.5) * transform.opacity;

}