If you are seriously interested in medicine you will need to go to a four year university or college and take certain courses. You do not have to major in premed but you will have to have a number of science courses including organic chemistry. You may also want to do research to become more competitive for medical school. Near the end of college you take an exam called the MCAT and apply to medical schools. It can be difficult to get in and many kids have to apply for several years.
Medical school is four years long and includes both courses and clinical work where you go into the hospital or doctor's offices and learn. You then apply to residency programs in your chosen field. This is done through a match process where you list your choices and they list you and you are matched to a program.
For pediatrics the residency is three years long. This involves working in the hospital and in doctors offices. You do get paid at this point but it is not much and you work long and hard hours.
If you want to do general pediatrics you then get a job. If you want to subspecialize in something like cardiology or gastroenterology then you do a fellowship which may be anywhere from 2 to 4 years. During medical school and residency you take various national tests to qualify for licensure in the state you want to work.
With respect to pay - primary care doctors which include pediatricians, internists and family practitioners do not make a lot of money. We work many hours with lots of responsibility for a comfortabe income. Specialists do make more usually. This seems to be changing with more of an awareness of the importance of primary care. One of the main problems is that many doctors have huge loans from medical school and spend much of their income in paying off loans.
The new health care that is emerging in this country is using many mid level practitioners. This includes Physician Assistants and Nurse Practitioners. This is a wonderful way to get involved in the practice of medicine without as long and expensive a training. However, the need for physicians will always be there and it is a great career if you dont mind working hard.