I don't really understand what you're asking.
Heres what I think you're asking:
Property 1: value = 500k loan = 250k
Property 2: value = 500k loan = 250k
If you drew Property 1 out to 80% LVR to pay down Property 2, you'd have:
Property 1: value = 500k loan = 400k
Property 2: value =...