All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad is His slave and Messenger.
It is forbidden for you to sell your land to those people as you know that they will use it to build a place of idol worship. Ibn Muflih said: “If a person sells or rents his house to a non-Muslim, then Al-Marwathi reported from Imaam Ahmad that it should not be sold (to him), as the bell will be tolled in it and the crosses will be erected in it, and he considered this matter [this sort of selling] as a very serious matter and he absolutely forbade it. Moreover, Al-Qaadi (Abu Yaa’la) said: 'It is not permissible for a Muslim to rent his house for someone who would use it as a Zoroastrian temple or a church.'”
Besides, the Fiqh Encyclopedia reads: “The majority of the jurists stated that a Muslim is forbidden from selling a land or a house that will be used as a church.”
For more benefit, please refer to Fatwa 85602.
Allaah Knows best.