Software nobody wants to touch
Plenty of businesses depend on an application whose original developer is long gone. It works, mostly. Nobody wants to touch it, the framework is four versions behind, and every small change is quoted as a rewrite.
We take these on. The first month is spent understanding what is there and writing it down — which is usually the single most valuable thing anyone has done to the system in years. After that it becomes maintainable again, incrementally, without the rewrite.