Record low mortgage rates have many homeowners looking to refinance. But come next month, borrowers might be in for a shock. Fannie Mae and Freddie Mac will be charging a new — and hotly contested — “adverse market” fee on refinanced mortgages.Record low mortgage rates have many homeowners looking to refinance. But come next month, borrowers might be in for a shock. Fannie Mae and Freddie Mac will be charging a new — and hotly contested — “adverse market” fee on refinanced mortgages.