[watmough]

Really interesting question.

As primarily a maintenance programmer by inclination, I'd not ever given the possibility of self-employment a thought.

However, if you need to be paid, you need to create value. So the answer to your question is to find someone to pay you to fix bugs in software that 1) they use and depend on, that may not be well-maintained, 2) that you have the source and all dependencies for, and 3) that they would trust your expertise in understanding their requirements whilst being at 'arms-length'.

To be honest, it sounds a bit difficult, but you might try looking for support / developer roles. These are often unpopular with developers that want to do the new shiny, but there's lots of $$$ in keeping existing software working with updated APIs, fixing bugs etc.

Or you could be a framework evangelist / fixer on site. That largely matches my current role, where my job is to ensure that a large customer is happy, and utilizing our framework-type software to it's best advantage.