I think you could reap financial rewards with these ink drawings. Your talent is gold. Just peruse Etsy - Your place to buy and sell all things handmade, vintage, and supplies
for a little while. Almost anything goes there. I think you'd fit right in.
In fact, your portrait of a friend's horse makes me think you may do well with commissioned portraits. I think it takes a stomach of steel though, I know it wouldn't be for me however. I would be so worried the customer wouldn't see their horse in my work or that I wouldn't catch their personality just right.
But that is all besides the point. When you move into paintings, be sure to post your work. I'm sure there are a few of us who would love to see it.