I understand that buildings have to (by law) use a fumigador monthly in the common areas of buildings, and also to offer their services to each unit in the building. It is my experience, in two buildings, and after several changes of fumigador, that their services make little difference. What they are spraying is mostly water and it very quickly gets washed off the surfaces they spray it on - usually the same day.
My advice is to go to the local ferreteria and by some plastic syringes of GelTek for cucarachas. Then squeeze some of the gel under benches, in cupboards, and in all the places cockroaches have been seen. They eat the stuff, then go back to their nest and die. Which is what you want. In a week or so all cockroaches will be gone. And mostly they will stay gone. If you see more, use some more gel.
This is a very cheap solution that is easy to apply. So why we pay a lot to fumigadores I don't know.
Good luck with your friend's apartment.
La Fleur