320. Collateral benefits.

320.     Collateral benefits.

There is no objection to a stipulation that a mortgagee is to have a collateral advantage1 provided that:


    (1)     it is not unfair and unconscionable2;


    (2)     it is not in the nature of a penalty clogging the equity of redemption3;


    (3)     it is not inconsistent with or repugnant to the right to redeem4; and


    (4)     it is not an unreasonable restraint of trade5.

So long as these requirements are met, there is no objection to a collateral benefit continuing after redemption, and no rule which permits the mortgagor to redeem merely on payment of principal,