[gregjor]

That's a fairly common freelancer specialty. I have done quite a bit of maintenance and fixing on legacy systems, so much that I got taken on by agency based on my willingness to work on legacy code. I rarely take on new development, too much risk. I wrote an article about maintenance programming a while back, possibly still relevant.

https://typicalprogrammer.com/the-joys-of-maintenance-progra...

My approach: get the (potential) customer to list their top pain points, in order of cost (financial or otherwise), then I work through those. You have discrete well-defined tasks and customers can attach a price/value much easier than they can for new development. Once you show results the work snowballs -- every company has a backlog even if they don't have it written down. Word of mouth does the rest. Technically you need broad generalist skills and the patience to read lots of code and documentation. And you need to offer alternative solutions -- not every software problem has a technical solution, some problems come from organizational or people conflicts.