Is working as a sales representative for a tourism company that markets via a "timeshare" system permissible, knowing that customers are convinced by being promised prizes, which then entails the purchase of a lifelong "timeshare," and the salary is a percentage of the contracts?

It is forbidden to promote timeshare contracts that are for a lifetime, due to the unknown duration in the contract. For the validity of a leasing contract (ijara), the duration must be known. Also, the wage must be known, based on the Prophet's (ﷺ) saying: "He forbade hiring a wage-earner until his wage is made clear to him."