Having some sort of expertise or knowledge in your field of interest can help you and other people. Someone always have problems that needs fixing or solved. For example, if you like the stock market, why not read some books on how to buy stocks cheap or at a reduced price. I read a lot of blog posts at the forum that I frequent. It gives me tips and strategies for my business.
Maybe you want to read something on how to save money shopping. You can buy products out of season. For example,
you can buy coats in March or April at department stores. They will be making room for the spring fashions, thus the reduced prices.