In confirmation of 在合同中的意思为“为确定。。。。起见”，所以这句话可以翻译为：

为确认该从属关系起见，承租人应随时及时签署任何业主可能要求的证书。

类似的用法还有：

1. Article 3 When filing an action or making defense, a party shall provide or confirm to the people's court his accurate address for service and fill in a confirmation of the address for service.

第三条当事人起诉或者答辩时应当向人民法院提供或者确认自己准确的送达地址，并填写送达地址确认书。

2. Otherwise, the contract comes about in accordance with, and with the contents set forth in, the confirmation of the order.

否则合同将根据订单中所确认的指定日期以及其中内容成立。