Unfortunately for many, one source of income is just not enough. Therefore you should consider picking up a second side job. I've listed some examples in this post. Keep in mind you can always do something you love as a second job - it doesn't have to be "work"!
For example, writing is one of my passions, and I just started blogging for InfoBarrel. I'm new so I haven't made any money yet, but you have to give it time. If you write about something you are passionate about, and if you write articles that will be useful to people, I think the money will follow. Some people on the site are making upwards of $2,000 a month!
Sign Up Today and start writing ASAP! I recommend you read up in the forum for help - the people here are very friendly and helpful to beginners.