Is it permissible to rent out a property built at a low cost for a large sum that equals properties built at a high cost, taking into account that this causes great hardship for tenants amidst rising rents and their impact on their lives?

The old rental system is Islamically void contracts, due to the unknown duration therein. The duration must be known, and the rent known and agreed upon by both parties. There is no prescribed limit for its amount in Islamic law, but excessive exaggeration that exploits people's needs is disliked. The Prophet, peace be upon him, prayed for mercy upon those who were lenient in their dealings.