How can I make my horizon/edge of my reflective floor either transparent or blended with the background, so you only see the RVs with shadows and reflections? So far all I've been able to do is set up more lights over the floor's background edge to blend in more, but I need it gone. I'm attaching a picture. I'm still new to blender, so please be specific. Thank you in advance.
The best way to make your floor blend into your background is to composite the two together from separate layers and feather the edge of the floor layer.
In the node network below I've used a Rectangular Mask node into a Blur node to create the blurred masked that is used to set the alpha channel of the floor layer.
In this image, you can see the size and orientation of the mask node (indicated by the white outline).
And the final effect:
This technique works best with still images, but can be used with animations if the floor edge does not move a lot in relation to the screen.