As a benchmark, I know that University of Waterloo Computer Science and Computer Engineering Co-ops are making $60/hour for similar work. That's a good starting point. If you have any kind of portfolio, you should be able to leverage that into a higher hourly rate. In finding clients, its important not only to build a portfolio, but also to build a network that can help you find new work with interesting clients. So if you have a portfolio of two or three apps, along with a few people who are willing to serve as a reference for you, then you should be on your way.