The interest in the direct loan sense is zero, but there is an implicit interest rate built into the price the intermediary buys and sells the asset for I.e a price differential. This can be used to calculate an implied interest rate.
It can be used not as a Null but as floating, linking the inflation with a gradient. Similar to inflation indexed bonds. DCF should produce the current NPV of a project, else the selection process will be incomplete and theoretical or in other terms that gain could be termed as " possible Capital Gain". However the effect will remain the same.