I am going to sound like my dad...
Hi jet_breeze,
At 15 you have the advantage of youth on your side. Before you go rushing off diving into CPL & ATPL questions, have a good look around this and other websites that cater for wannabes.
Consider what subjects you should be studying at school, GCSEs and A-Levels for example. Consider what degree you should study after school. Consider choosing a University that has a University Air Squadron. Chances are you will need to earn some money first before you can get the required financing for a CPL/IR and ATPL ground exam course. A good education will always ive you something to fall back on if the flying doesnt work out.
Formulate a long term strategy for gaining first your PPL, 17 is the minimum age. If there is a local Air Training Cadets or Air Scouts group close by think about joining them. Consider joining a gliding club, it is much cheaper and you can build some very valuable flying skills for a fairly small amount of money, which will stand you in good stead in the future.
Buying a share in an aircraft such as a 182 is not a cheap proposition. First of all the rest of the share owners will need to approve you, and for someone so young insurance may be a problem. You will probably have to buy a share for around 8-10k plus monthly subscriptions for maintenance and a contingency fund, plus hourly flying costs (fuel, insurance landing fees etc). Your parents will need to increase your pocket money a bit!