What does it take to become a professional poker player

First we should set how we define the term "professional poker player".  A professional is someone who derives the bulk of their income from playing poker.  If you have just $1,000 in monthly expenses and are able to pay these from playing poker, then in my book you're a professional.  If you make $5,000 a month from poker but have $20,000 in expenses, then I would not consider you a professional poker player.  Though you are certainly a very skilled player, you don't pay the bulk of your expenses with your poker earnings--you have some other means.  You're making $15,000+ a month from some other source.  That is your profession, not poker.

Now that we've defined what exactly constitutes a professional poker player, let's discuss what it takes to get there.  The most obvious starting point is a ton of practice.  Just like any other profession, you're going to need to dedicate time and educate yourself.  This may be in the form of training videos, reading books, or the old fashion learn-through-experience.  It likely will take a combination of these to get your skill-set where it needs to be.

Next, you need to work on controlling your emotions and staying mentally sharp.  There is a large element of luck in the short run and you're guaranteed to have losing sessions, losing days, and even losing weeks and months.  You need to be able to handle these downswings and not let them affect you emotionally.  If you lose your head, you'll likely lose more money than you needed to.

You're also going to need a bankroll.  If you're playing tournaments where you've estimated your largest likely downswing to be 200 buy-ins, then it's advisable to have 250+ buy-ins for a comfortable bankroll.  You'll be able to withstand a significant downswing and it will mentally affect you less as you see your downswing is a lower percentage of your bankroll.

Lastly, you need to set a schedule.  If you expect to pay your monthly bills by playing poker, you have to realize that your hourly is not constant.  You may average $50/hr, however that is going to drastically fluctuate on a day-to-day basis.  Not only are you going to want to have 3-6 months worth of living expenses in your savings in case of a downswing, but you'll want to set a schedule and play regularly so that you have the greatest chance of variance evening out in the short term.  As your sample gets larger, you'll get closer to your true win-rate.  You need to be putting in volume to decrease the likelihood of a losing month.

Once you've got these steps down it's important that you keep up with the ever-evolving game of poker.  Dedicate time to reviewing hands, posting on forums, and discussing strategy with people you respect.  Your bankroll will thank you.