Just start, it is not complicated business. Ask around for work, deliver results and repeat. If you are any good you should be fine. Start with doing side projects and then make jump if you like it.

On the other side, there is no certainty in freelancing, programming will be just some part of your job and most of your time will be spent on trivial projects (unless you are very lucky).

I am 12 years into freelancing and it is good way to make living.