I've looked a little at some of the sites like ODesk or Elance but all the job listings I saw there and the bids offered were a joke.
It seems like the rates on Elance wouldn't be sustainable.
I've had several clients who had bad experiences on elance and other sites (undelivered work, bad developers etc). They decided to give it one more try and hired me. They don't want to risk the bad experience again and are willing to pay more to continue working with me (and we work outside the freelance sites from that stage on). It's an expensive and timely process to find a good developer so once clients find one they like to stick with them.
If I never used these sites I think it would be pretty difficult to ever find clients. Most of my other clients come through recommendations by clients I originally found on elance etc.
You can see the apps I've made so far here: http://www.plastaq.com
So I can't really offer you specific advice on finding clients except for maybe to think of your own apps as pieces of a portfolio as much as sources of revenue on their own.
I'm currently living and working in Vietnam so at the moment I'm charging my clients a lot less than the $150+/hr a good iOS dev can get in S.F. or New York but my living expenses are a lot lower here and I hope to gradually increase my rates for new work as I build a roster of clients.
Working on my own apps is more fun, of course, but actually making money is a good thing too.