翻译：根据制度,你必须预先付一个月的房租.(in advance)

According to the constitution,you must pay for a one-month rent in advance.

According to the policy, you have to prepay rental of one month.
楼上回答的语气太生硬,这样会给客户气跑的.

according to the regulations(or rules),you have to(or shopuld)pay for one-month's rent in advance.
此处,“必须”并非主观意愿,因此使用“have to”或“should”更好一点