The Complete Trilogy from SF author Hugo Krait.

In the independent city-states of the year 2031, you're always better off not getting involved.

Burly robot repairman Mack Sullivan tries hard stay out of trouble, focusing only on his work and his next meal. Haunted by the loss of his sister, Samantha, a drug user who died during the privatization era, Mack concentrates on fixing up and recycling old robots, many of which are being used for security within the walls of the sovereign municipality of Rockridge.

But a single decision sends Mack on a mission that will bring him up against the richest and most powerful figures in town — and which will send him outside the city walls for the first time since the start of the privatization era, on the trail of a ghost that has haunted him for a decade.

Mack Sullivan tried hard not to get involved. But he’s definitely involved now.