I think some of you are a bit rude to the OP here. "Why do you want to become a professional" and so on. Actually, your choice of your profession is nobody else's business.
So, what do you need in order to become a professional? Well, a good teacher might be good, like someone here suggested. There are many professional pianists who take students. I'm not talking just about famous concert pianists here, but about studio musicians etcetera, who take students because they need the income. And those people are good to have in your contact network, because they might lead you to jobs and gigs. You have to be prepared to play "anything", so your repertoire must span over many different genres. I also suppose you must be prepared to play for free, or for very small fees in the beginning.
So, can you improvise? Are you good at accompaniment? Do you have a solid repertoire of well-known, contemporary pieces, jazz pieces and so on? Can you join a band who needs someone at the keyboard? Can you play country, rock, gospel ...? What if a music store or a manufacturer wants someone who demonstrate new products? If a senior home, an orphanage or a hospital asks you to play at their annual Christmas Party, and your salary will be a meal coupon at McDonald's, will you do that?
All these things will finally make you a professional, there are many musicians who make a living out of this. (Actually: most of them, just as most actors make a living from commercials and voicing cartoons.) You should also consider learning piano tuning and teaching, of course!
Except being a good musician I simply think you need to be innovative when it comes to job opportunities, and don't consider yourself "too good" for certain kind of jobs. Well, this does not mean you have to become a total prostitute either, of course. If you don't feel like playing at strip joints or at political meetings you hate, then don't ... Oh yes, we have all seen the cliché movie scenes with a poor struggling actor/singer/musician who is forced to entertain some little ungrateful monsters at children's parties and so on. Well, you will never be a slave - hopefully - so if an offer does not please you, then decline it.
If you don't think my description above sounds fun, if you just want to play in the big concert halls around the world, well ... then go and find yourself an agent!