I have a question regarding property advisory.
Recently I bought a plot on installment basis for my cousin. Plot down payment was 135000. I was in contact with marketing agency, they told me on my regarding they will take 90 thousands as down-payment and the remaining amount is my commission, they did that discount for my commission purposes otherwise the normal down-payment is 135000.

My question is do I have to let my cousin know about this. If I tell him may he demand some amount from my commission. If I do not telling him, then what will be rule for this in Islam. Is it halal or haram?

If this is your business and you buy and sell property, and your cousin if one of your normal customers, and it’s expected that you make a profit from a sale and this is known by people (ie not hidden) then you don’t need to tell him. Otherwise you must tell him as it will be deception.