Would this little scheme be halal?

Riba is haram, and an interest-based mortgage is haram. But what if I carry out the following transaction: I enter into an agreement where a person buys only one room of my apartment but gets to use the entire property. They move in and live there, but legally they only own one room. After a few months, as stipulated in the contract, they are obligated to buy the second room from me. I will offer it at a new price, factoring in inflation and adding my own margin. I’ll repeat this process for the remaining rooms. Would this be considered haram? On the surface, the conditions have changed, but in reality, it’s the same as a mortgage where a flat costs, say, 20% more because of the installment plan. In this case, the apartment also ends up 20% more expensive for the buyer because they signed this specific contract.