(a) All contracts made and entered into by and between the borrower and lender, debtor and creditor or mortgagor and mortgagee, on which the rate of interest is six per centum or under, wherein one party agrees to pay the taxes on the debt, credit, or mortgage existing or entered into between such parties, are legal and valid and shall not be deemed or taken to be usurious.
(b) All contracts of the type described in subsection (a) of this section may be enforced by the parties thereto.