Firstly, I think there is a mistake in the filters for both the KFs:
Rent Amount: <=Repl rent valid from and >=Repl rent valid to and same for Area occupied: <=Repl area valid from and >=Repl area valid to
This conflicts with what you wrote earlier: it should be Rent Amount >= Repl Rent valid from and <= Repl valid to etc.
Also, you need to apply a constant selection restriction on the Rent Amount (for Area Valid From=# and Area Valid To=#) and on Area (for Rent Valid To=# and Rent Valid From=#)
Why you need to do that is explained in the "Multiprovider Problems" section here: Constant Selection - Business Intelligence - SAP Library