Personally, my reservations with charging are two fold:

1) That I come from the open source community, where charging is successful and the value of your code is often personal rather than looking at the user's value. Also, much of my knowledge of coding has come from reading others' code, does this mean whatever I create is an extension of their creations, which they offered free of charge?

2) That I wasn't sure I was good enough to charge. If users started paying money and my database went down when they needed it most, how would I respond? I'm not a legal expert or even a trained business person.