Carlos, you are not too old to change carers and become a commercial pilot. I am your age and I am just starting my commercial pilot career as a part time flight instructor building hours to get a good corprate pilots job.  I would recommend starting out in a single engine and then progress to the multi engine not only will it be cheaper at first but it will help you when you get into the time building phase of your career because the best way to build time is to be a flight instructor. I would recommend a structured program unless you have a friend who has a plane he will let you use and also has his instructor rating you would be waisting your time. If your goal is to become a career pilot I would recommend one of the more structured schools that take you from private to commercial for a set price and have some connection with the airlines.