Legal to download a photo or graphic, sketch it myself, then re-sell the outcome on merchandise?

What I mean in the title is, if I downloaded a digital graphic of a hot air balloon, and then sketched that image myself in a different style (pencil sketch style), could I re-sell the outcome even though the fundamental shape etc. would be extremely similar?

I just read that you can re-sell stock images from Envato, as long as you add creative elements to the outcome, just wondering if this would be enough to meet that requirement?