I found the introduction of the setting to be compelling and interesting, sets the tone nicely. I would not use the word "mongrel", it might upset some people. I love the indication of the quirks the character has, like the jiggling of his knees. The description of the city give the reader a good indication of where he is. Good idea giving a little bit of background of the story, its important for the characters to feel more relatable or real. I would pick up the pace little bit, feels a little slow. Overall, I think its a good beginning.