Those who wait until they are earning more discover that they never seem to be far enough ahead to save. Each higher level of income is met with a higher level of spending. In the beginning, it is not how much you can save but developing the discipline to save that is important. Even saving small amounts early in life is beneficial because it helps you develop a habit of saving that will become second nature. Saving early is also important because with compound interest, time is a young saver's best friend.
Time is money.
Now you probably already knew that you should pay cash and start saving early. I have read and would like to recommend several good books on this subject. The following books approach saving and living within your means from a variety of angles. Find one that suits your situation. Personal Finance in Your Twenties and Thirties.