In the movie: Leon, the Professional, the actual quantities of money spent on drugs were not discussed.
We do note that the price Leon was paid to kill drug dealers was mentioned, and that Matilda who had no money offered to be his live in help.
This is not a fantasy, but something that occurs every day over and over in our world.
Had Leon been a cruel or careless man, this relationship could have gone in a different direction and would have been called "human trafficking."

HYPOTHETICAL: an addict who buys one hit of horse a day at $50 a hit, is spending $15,000 a year on horse.
In a geographical area where the price of one hit of horse can run up to $100,
even that conservative estimate of $15,000 could pay the mortgage on a house large enough to comfortably accomodate 4 people ages 14 and older.
Thus, one addict who is cured could mean housing for four to eight people.
These are numbers.Neocities.