Ruling on renting out his share of the shop to his partner
Question

                What is the ruling on renting my share of a shop to my partner or to someone else for a fixed amount every month?.
Praise be to Allah.
      If a person has a share of a shop, it is permissible for 
      him to rent it out for a fixed, known amount, to his partner or to someone 
      else, according to the basic principle that it is permissible to rent out 
      houses, shops and other things which may be used and benefitted from and 
      still remain. Renting something that is shared with a partner is 
      permissible according to scholarly consensus. 

    Ibn Qudaamah (may Allah have mercy on him) said in 
    al-Mughni (5/317):

    Section: What it is permissible to rent or hire out. It is 
    permissible to rent or hire out anything that can be used in permissible 
    ways but still remains, such as land, houses, slaves, animals, clothing, 
    pavilions, ropes, tents, bags, lamps, reins, swords, spears and so on. 

    In al-Mawsoo‘ah al-Fiqhiyyah (1/263) it says: Renting 
    or hiring out items of which ownership is shared with others: if the item in 
    question is shared and one of the two partners wants to rent out the benefit 
    of his share of it, then it is permissible for him to rent it out to his 
    partner, according to scholarly consensus. With regard to renting out to 
    someone other than one’s partner, then according to the majority of Hanafis, 
    Shaafa‘is and Maalikis, and according to one report narrated by Ahmad, this 
    is also permissible, because renting or hiring is one kind of transaction, 
    so it is permissible to rent out shared property just as it is permissible 
    to sell it, and shared property may be benefitted from by turns [i.e., each 
    partner may benefit from it for a certain period]. Hence it is permissible 
    to sell it. It says in al-Mughni: Abu Hafs al-‘Akbari favoured the 
    view that it is permissible to rent out shared property to someone other 
    than one’s partner. Ahmad suggested that, because it is in his possession 
    and he could rent it out to his partner, therefore he could rent it out to 
    others, like selling. And because it is permissible if both partners do that 
    together, so it is permissible for one of them to do that with his share on 
    his own, as is also the case with selling. End quote. 

    Conclusion: it is permissible to rent out your share of the 
    shop on its own, or with the fixtures and fittings that are in it, such as 
    equipment, shelves and so on. 

    With regard to your share of the goods – if applicable – it 
    is not acceptable for you to rent them out, because renting is a contract 
    that has to do with benefitting, and goods can only be benefited from by 
    selling them; rather the goods are to be evaluated and sold to the renter, 
    if he wants that, even if it is by instalments. 

    It is permissible to delegate him to sell them, for free or 
    in return for payment, according to whatever you agree, or you can take your 
    goods and sell them to whomever you want. 

    And Allah knows best.