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.
The solution to your second reservation is to have users agree to a software license/terms of use. Usually, there is no guarantee of uptime. If you want to guarantee uptime, then you can do that. In that case you'd define the terms of your guarantee to be something like, say, $10/day of downtime up to the amount of the monthly bill.
The solution to your first question is to realize that all professional developers have learned from other developers. It's a pay it forward system. Someday, someone will look at your code or receive free advice from you that helps that person make a living off of software. That said, if you think you are deeply indebted to a particular person, you could thank that person with a monetary gift or even purchase rights/license to use the code.
The solution to your first question is to realize that all professional developers have learned from other developer
All professional anything have learned from others: teachers, doctors, lawyers, authors.... It's how society gets better. Business is the engine that powers it (even if indirectly), and money is the fuel that allows it.
There's absolutely no harm in charging for something of value you create because of what you have learned. Besides, you can always give back to the open source community- maybe even moreso if you are in a position to provide a little funding for some projects (because you charged for your product).
"... does this mean whatever I create is an extension of their creations? ..."
Yes it does. Everything ever created is an extension of what someone else created. And someone may create something new based partly on learning from you. Don't worry about it.
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.