Depending upon various factors, it could be either lawful or unlawful to lease the shop to another party without the permission of the owner. When the owner has the right to get the premises vacated or to increase the rent, but the tenant neither increases the rent nor vacates the premises, it would be unlawful to use the premises or to lease it to another party. And in all those cases in which the owner of the property does not enjoy the right of increasing the rent or getting the premises vacated and the tenant is entitled to vacate the premises for someone else, it would be lawful to take key money, equal or more than what he pays to the owner, without the owner’s permission.   _{Your Comment}