In the Novel, he is a Mathmatical Wizard (not the same as a Magic Wizard). At the start of the Novel it is said he did the Government a great favour by getting rid of the National Debt so, as a reward, was let off his income tax for life. He was also provided with a house on the outside of Regents Park.
According to the Novel, whilst not exactly handsome, he doesn't have a face you would tire of. It is said Pongo could of been a show dog, if Dog Shows didn't bore him.
When the Puppies are born, Mr. Dearly takes it upon himself to feed them, coming home early from work and getting obsessed with helping them. He is disappointed when they adapt Perdita, since he isn't allowed to help feed them after that.