In addition to the charges authorized by section 838 or 839, a licensee may contract for and receive an administrative fee, that must be fully earned immediately upon making the loan, with respect to a loan of a bona fide principal amount of not more than $2,500 at a rate not in excess of 5 percent of the principal amount, exclusive of the administrative fee, or $50, whichever is less, and with respect to a loan of a bona fide principal amount of $2,500 to $50,000, at an amount not to exceed $75. No administrative fee may be contracted for, or received in connection with the refinancing of a loan unless at least one year has elapsed since the receipt of a previous administrative fee paid by the borrower. Only one administrative fee may be contracted for or received until the loan has been repaid in full. For purposes of this section, “bona fide principal amount” must be determined in accordance with section 885.