I did so for a few years during college. It is possible if you put in the time and effort and are of at least average intelligence. You must have good bankroll management, control over your emotions, and the time to play. It is NOT easy. It is utterly frustrating at times and can be very demoralizing. You are always trying to make money from others who may be working just as hard at their game to make money off you. You must stay ahead of the curve and be constantly looking for the best games. Studying hand histories is a must. Reading/posting on the 2+2 forums is nearly a must. Subscribing to a video site is nearly a must. Getting a coach is nearly a must.

Supposedly about 10% of players are winners. Of those, only the ones who put in lots of hours, control themselves, and rise to reasonable stakes can make a living.

Also, it depends on what you mean by "a living". If you mean you need to get by with a part-time equivalent income for a few years, then it isn’t all that hard. If you are looking to make a long-term career out of it, unless you are verry smart, verry determined (addictive personality), or flat out crazy, I would look elsewhere. The poker bubble has come and gone and players are mostly decent by now. The catchup curve is quite large by now and the higher stakes games take lots of dedication and smarts to break into. More importantly though, is that there is no guarantee that poker, as profitable as it has been and still is, will be around in 5 years. Do you want to take that chance? It might work out, but for a vast, vast majority it won’t work out to be a long-term, profitable, and HAPPY career that most think it will be. It can be lonely, unhealthy (both physically and mentally), without benefits (insurance, etc), and ultimately a zero on your future resume.

Btw, if you are doing it for the money, ultimately being a good entrepreneur will be much more profitable. Many poker players realize this, such as Hellmuth and others that actually make a bulk of their income from business interests and play poker for the fame, success, and enjoyment.