I'm interested in doing something similar myself. If the HN hivemind could help out, I have a few questions:

1 - How important is it to have some sort of public profile (eg, High ranking StackOverflow account, Github account, well trafficked blog) or public portfolio? I've done lots of good work as an employee but almost all of it is on internal corporate networks.

2 - Where do you find the all important first few customers? Should I be going to every local users group I can find and handing out business cards? Or hitting up sites like http://www.guru.com/ ? What worked for people?

3 - What size jobs are feasible? I would like to start this on a part time basis while still working my day job. Is it possible to find jobs small enough to keep me working 1 or 2 days a week?