Is it permissible for us to take money from him for his renting or is it better to let him live in our flat without receiving this amount of money monthly ?

In the Name of Allah, the Most Gracious, the Most Merciful.

As-salāmu ‘alaykum wa-rahmatullāhi wa-barakātuh

Answer:

In principle, it is permissible for one to rent out one’s property to one’s relative. However, if you and your husband mutually agree to forfeit the full rental or part thereof, it will be an act of charity.

Consider the following Ahādīth,

الصَّدَقَةُ عَلَى الْمِسْكِينِ صَدَقَةٌ، وَهِيَ عَلَى ذِي الرَّحِمِ اثْنَتَانِ: صِلَةٌ، وَصَدَقَةٌ

Charity given to the poor is one and charity given to a relative is twofold, maintaining ties and charity. (Musnad Ahmad, 170/26)

مَنْ سَرَّهُ أَنْ يُبْسَطَ لَهُ فِي رِزْقِهِ، أَوْ يُنْسَأَ لَهُ فِي أَثَرِهِ، فَلْيَصِلْ رَحِمَهُ

Whoever likes to have increase in his sustenance and to live long, should maintain ties with his relatives. (Saheeh Bukhari, 4/490)

And Allah Ta’āla Knows Best

Ismail Desai,

Darul Iftaa

Checked and Approved,

Mufti Ebrahim Desai.