SH4-D0 was originally purchased as a new model holodroid "toy" for a very rich child. He was long in a line of holodroids purchased as "toys" for the children. The child and family were fine, not especially nice or especially poor conditions. Just average. SH4-D0 had no complaints, and neither did they. When the newest model of holodroids were released, the family did as they'd been doing since the kid's birth and bought him a new one. The old one, SH4-D0, was simply powered down and thrown away (they couldn't be bothered with recycling or selling him).

SH4-D0 awoke in a junkyard as scrappers were stripping him for parts. He lost all the abilities of his original holodroid programming.

SH4-D0 wanted to build himself back up. As he walked the streets of Nar Shaddaa, he realized credits were the first step if he was going to pay mechanics or programmers to help him.

SH4-D0 pretty much goes after the first job he sees, which in the underbelly of Nar Shaddaa, is drug running. Korra eventually finds him as she's looking for runners for Saffron Moons and decides he's perfect (since he won't sample the merch, etc.) and enlists him to be one of their runners.

Credits (EotE:95) - Money is the prime motivator for SH4-D0.

Obsession: SH4-D0 is obsessed with getting credits. He must pursue this, to the detriment of his well-being (like being a drug runner does). He tends to get along well with others that share his interest, but is looked at with pity, amusement, or even a bit of fear from others who don't understand.

SH4-D0 looks like a regular, standard, cookie-cutter droid. He has arms and legs and stands upright.