If one thinks about it enough, what is the requirement of being a pianist? Being able to play the piano. Depending on how much you want to invest in it, you could certainly become a pianist. As far as recieving the PROFESSIONAL training usually required to become a concert pianist ,at age 33 most conservatories wouldn't acept you (the cut-off is usually 21). This does not mean that you can't play as a career though, at 33 you are still young and I took piano for only a year and a half before I was accepted into a conservatory as a piano performance major, that being said, say in a few years time, you decide you are ready to make the next step, you could work on a cruise ship as a musician, you could play in bars or clubs, you could join a band.
You may be headed in the other direction though, maybe you want to play classical piano. In that case, the only requirement of playing on a stage in front of a large group of people is to know something that they want to listen to. Once you get to that stage, the pieces will automatically start falling in place.
Good luck to you! I wish you well on your musical adventure! And never, ever forget that no matter what, if you want to do it, you can do it. I had people tell me that I couldn't get into music school and I proved them wrong. So prove anyone wrong who says you can't become a pianist at 33.