Even if you have a full time job, you can consider this as an extra income option as you can use this money for other expenses like purchasing a music player, going for a vacation etc.
Using online business you can decide how much money you want to make and the best part if you are the boss. There are many options and opportunities available for earning online. While some of them are free others require little investment to do a kick start.
The first thing that you want to do is set a goal for yourself. Understand why you want to do some online business. Do a little research in the domain you are a going to choose. Analyse the revenue part. Once you are done with the initial analysis, forget about it and start working. You can hire professionals who can SEO and internet marketing for you till you get comfortable in that.
Have a happy earning money online !!