What is the best paying, yet enjoyable jjob choice for a sketch pad artist?

I'm not sure what you mean by a "sketch pad artist"; I'm assuming your talking about someone who draws on paper for a living? Well, there are illustrators for magazines, publishing houses, advertising companies, businesses and so on, so that would be an option. Usually this is on a freelance basis, where there is a lot of competition and the money to start is usually not very high, but it can improve with experience and increasing skill. Of course, there are many careers where sketching out ideas on paper is a first step, such as fashion designers, interior decorators, architects, product designers, graphic designers, etc. etc. In these areas, having an artist to do some finished sketches is useful, for example fashion designers, interior designers, architects may want finished sketches to show potential clients. Again, this would probably be on a freelance basis. So, you might want to narrow down your ideas as to what type of drawing you like to do....People? Buildings? Furniture? Cars? Insides of electronic devices? Landscapes? Remember, the best job in art is the one you are qualified for and one that fits your interests.
However, please understand that computer generated drawings are the wave of the future. Many illustrators and artists today use and combine both traditional art materials and computers to make their art. I suggest you take some computer graphics classes to get familiar with this exciting and creative art form. I taught a class in my Middle School which where my students were introduced to making artworks on the computer using Paint and Photoshop, and they all really loved it. I strongly suggest you talk your art teachers at your school about your questions. If you have a career center in your local High School, I suggest you go there for some information about art fields in general. Good luck and keep drawing!