In this scenario,
$image = media_sideload_image($downloadable_path, $post_id);
The $image variable now returns the full HTML, like this (with single quotes for some reason)
<img src="http://www.somesite.com/wp-content/uploads/2012/11/image8.jpg" alt="" />
Which isn’t so bad, unless we want to get Just the image URL, or maybe the Thumbnail URL, or just the attachment ID.
Here is how to do it.