Is it permissible for the owner of a building to rent a shop to a pharmacy that displays a crescent and a cross on its facade, and what is the ruling on working in a shop within the same building?

The cross is a symbol of disbelief (kufr); it is forbidden to display it, and it is obligatory to break and efface it. Ibn al-Qayyim and Ibn Umar ibn Abd al-Aziz prohibited Christians from displaying it.

Placing a cross on a pharmacy is not permissible. However, in cases of extreme necessity, such as people needing the pharmacy or the owner needing the rent, it is permissible to rent out the premises with the cross present, because its presence is secondary, not fundamental, and because it can be effaced.

This applies if the placement of the cross is mandatory by the responsible authorities. If it is optional, then it is not permissible under any circumstances. Working in another shop in the same building is permissible.