Build up a portfolio
Without a network to start with, you'll need a way to convince potential clients that you are worth hiring. The best way to do that is with a portfolio of previous work to demonstrate your skills.
Secondarily, a portfolio that includes actual clients will serve as a list of references too, in case potential clients ask for them.
If you don't have a portfolio, here are some tips on how to build one:
Strengthen your reputation
Your reputation is one of your most valuable assets. Go above and beyond in helping each of your clients, whether they are non-profits, from Elance, or elsewhere. This is key. If you are viewed as simply an execution shop, they will view you as a commodity. If you provide services well beyond what they are asking for, they will view you as exceptional.
You can also work to establish yourself as a knowledge source in your industry:
Grow your network
Now it's time to start growing your network. All networks take time, so be patient and aim for quality over quantity (since you're a one-person shop, it's better to have one great client than three horrible ones).
Once you have a larger portfolio of completed projects, testimonials, and references, it will be easier to go after larger customers.
Step one is to build a portfolio. People you meet to be able to see that you can do the work. Start some sideprojects, make things related to interests you have, etc.
Then pick up Craigslist work where you can, look for local mailing lists and job boards where people may post contract work, set up some saved searches on twitter for people looking for someone with your skills, etc.
Simultaneously and most importantly, build your network. Go to events & conferences, join meetup groups, get active on twitter and LinkedIn. You'll both meet the occasional person who's going to those events because they're looking for a contractor, and make connections with peers and folks who don't need your services, but can refer you to people who do.