Is it permissible to seize barren desert land that no one owns and cultivate it for sustenance and selling crops, while claiming ownership of it for years to facilitate the procedures for obtaining official documents, given that there is no other source of livelihood?

The questioner did not specify who is responsible for the land, whether he is appointed by the state to preserve it for future projects or not, and why he takes the money. However, the answer will be based on certain assumptions. The issue pertains to the revival of barren land (iḥyāʾ al-mawāt), which is land that has no owner and to which no protected ownership interest is attached. If the land is properly revived, it belongs to the one who revives it, even if the ruler has not given permission. This is the view of the majority of scholars. The proof for this is the saying of the Prophet, peace and blessings be upon him: "Whoever revives dead land, it belongs to him." As for claiming possession (wadʿ al-yad) before revival, it is not permissible because it is a falsehood. However, if it is after revival and there is no other way to prove the right except through it, then lying for a legitimate religious benefit is permissible.