can one making a living off furry art? yes and no... Depending how good you are, how you manage your time/money/costs, how well you advertise, and how diversified you are, you CAN make a living doing furry art.
However, it is very hard.
An artist needs to be good enough or have a unique style that will be in high demand. They need to be flexible - just selling at cons won't make the big bucks, but if you are willing to sell original art/prints/booklets/comic books/posters, and are willing to branch out into fields such as children's book illustration, comic books, role playing game guides, character design for video games or animation you can manage. An artist needs to know how to manage a business, advertise their skill set to the right market, and know how much money their time is worth and act accordingly. An artist also needs to know how to manage their time to meet deadlines.
I wouldn't jump out and quit my day job to become a full time artist though, as you can see it's a lot of hard work. One would have better luck as a full time artist if they did not limit themselves to simply furry art. The more adaptable an artist is, the more they can branch out their skill set into other fields of work.
As for untapped markets, there are many reasons this happens... yes, sometimes the subject matte just doesn't interest the artist... but also, they may have tried a few in a particular style and found it sold poorly compared to other art, so they chose not to waste their time making art that sold less than popular subject matter. I find different art sells better or worse at some cons, so I select my portfolio accordingly when planning for the con. This way I can sell more art I know will sell and have less to carry home at the end of the day.
