Is it permissible to subscribe to a website for selling mobile phone applications for a fixed annual subscription and 30% of the sales profits?

If the contract between the questioner and the website is a lease contract with a fixed rent and a percentage of sales profits, then it is not valid according to the majority of scholars, such as the Four Imams, due to the uncertainty of the rent. Both the compensation and the work are unknown, and the presence of a known amount of money alongside an unknown percentage does not make it permissible. For the validity of a lease, it is stipulated that both the benefit and the rent must be known, in order to prevent disputes.