You're never too old to start playing. In terms of the level you can achieve, it's a very difficult sport and there are many levels. All you can do is find a club, have a knock about, maybe get a few lessons then it's all down to practice. You'll find your highest break getting bigger over time and once you can knock in 30 and 40 breaks you'll be a decent club player standard.
All these pros you see on tv will have been playing for years and will also have a natural ability. You won't know until you give it a go basically, but if you're knocking in 60, 70, 80 breaks within the first year of playing then you have a serious talent.