Just becuase there a lot of properties on the sale market does not mean resnt will go down on average over the whole rental market. It could mean the opposite as those who lose their homes and the increasingly large number of patientlywaiting need somewhere to live and the supply of properties for rent might jsut be reduing as landlords are nervous to add properties yet to their portfolios.
The bottom line…..have you researched the rental market and its dynamic in the that area . maybe that area will be weak while the rest is strong for a special reason.