Fagin is an interesting character. He does create a home for the boys, his apprentices, but he expects a lot in return. When Dodger comes across Oliver, he tells him he can give him a place to stay.
I know a 'spectable old gentleman as lives there, wot'll give you lodgings for nothink, and never ask for the change--that is, if any genelman he knows interduces you. (enotes etext p. 37)
It's a trap, of course. It does seem that part of Dodger’s job is recruiting unsuspecting youngsters. Fagin teaches the boys to be pickpockets by playing games, and seems to treat them largely as adults as long as they keep bringing in goods.
It’s not the lap of luxury. Fagin’s den is first described this way:
The walls and ceiling of the room were perfectly black with age and dirt. There was a deal table before the fire: upon which were a candle, stuck in a ginger-beer bottle, two or three pewter pots, a loaf and butter, and a plate. In a frying-pan, which was on the fire, and which was secured to the mantelshelf by a string, some sausages were cooking. (p. 38)
As grimy as it seems, there is food and warmth. Oliver is relieved of anything he might have of value and given liquor as soon as he arrives, along with the food.
Fagin is clearly abusive, however. He is usually described as “villainous-looking” (p. 38) and sneering. He threatens and beats the boys on a regular basis, and withholds food, especially if they return empty-handed.
Whenever the Dodger or Charley Bates came home at night, empty-handed, he would expatiate with great vehemence on the misery of idle and lazy habits; and would enforce upon them the necessity of an active life, by sending them supperless to bed. On one occasion, indeed, he even went so far as to knock them both down a flight of stairs; but this was carrying out his virtuous precepts to an unusual extent. (p. 43)
Although Fagin does not seem to hit them hard most of the time, he did throw Dodger and Charley down a flight of stairs. Dodger is clearly afraid to tell him that they lost Oliver, and when he does Fagin threatens to throttle him. Sikes walks in on it and comments:
What are you up to? Ill-treating the boys, you covetous, avaricious, in-sa-ti-a-ble old fence?' said the man, seating himself deliberately. 'I wonder they don't murder you! I would if I was them. If I'd been your 'prentice (p. 59)
This highlights the precarious and violent existence of all of them. Fagin treats the boys cruelly, but they expect it. He has to keep the upper hand to get them to do what he wants. Sikes clearly thinks he is abusive and exploitative, but such is the criminal life!