Is it halal? Being a broker and selling property to non muslims knowingly that the non muslims use the banking system which is based on interest or riba i. E that they take loans based on riba to buy a property. Is the income from selling property to non muslims which is in the form of a commission halal?

All perfect praise be to Allah, The Lord of the Worlds. I testify that there is none worthy of worship except Allah, and that Muhammad, is His slave and Messenger.

You mentioned in your question that your work as a broker would be limited to selling property and the like of lawful things. If this is the case, then there is nothing wrong with that or with your earnings from it. The fact that most people in that country take interest-based loans to buy property and that the buyers often pay with the money of interest-based loans; this does not affect the permissibility of working as a real estate broker and mediator in the sale transaction. This is because you engage in a lawful transaction with the seller and buyer, and you do not act as a mediator in a sale of a prohibited commodity or guide them to it. The fact that the buyer borrowed the money through an interest-based contract is his own responsibility, and it is permissible for you to deal with him using the money that he possessed through Riba, especially if he is a non-Muslim. The Prophet used to engage in financial transactions with the Jews. He used to buy from them and accept their gifts although they consumed usurious interest. Ibn Al-‘Arabi said in Ahkaam Al-Qur’aan: “The most correct view is that it is permissible to engage in financial transactions with them, despite their engagement in interest-based transactions and committing what Allah, The Exalted, prohibited them from doing. This is established with decisive evidence from the Quran and Sunnah … It was narrated that ‘Umar ibn Al-Khattab was once asked about taking the price of Khamr (intoxicant drinks) when collecting Jizyah payment and when trading, and he replied, ‘Leave them to sell it and take from them one-tenth of the price …’” [End of quote]

Allah Knows best.