Ask HN: How do I take freelancing from a hobby to a career?

Over the past few years, I've had the chance to work on a few freelance web app and design projects, and I've become increasingly interested in the possibility of going from a hobbyist freelancer to a fully self employed developer.

All the clients who I have done work for the past are generally people I've met through Reddit, but none of them are the types of clients who have ongoing work or others people they could refer me to. Most of them are simply looking to get their web/mobile app developed (paying for it out of pocket), hoping that it will help them find funding. Quite a few even abandon the project a few weeks after I deliver it to them. How should I go about finding more professional clients to turn this from a hobby to a career?