Kyle Rizdahl

The president says that'll push mortgage rates down.

The president says that'll push mortgage rates down.

And indeed, in the time since, average rates on 30-year fixed mortgages have ticked slightly lower.

And indeed, in the time since, average rates on 30-year fixed mortgages have ticked slightly lower.

That's according to the Mortgage Bankers Association.

That's according to the Mortgage Bankers Association.

Although, to be clear, they had been trending down before the president's announcement, too.

Although, to be clear, they had been trending down before the president's announcement, too.

Nonetheless, Marketplace's Justin Ho looked into how mortgages become mortgage bonds and what will happen if Fannie and Freddie do wind up buying $200 billion worth of them.

Nonetheless, Marketplace's Justin Ho looked into how mortgages become mortgage bonds and what will happen if Fannie and Freddie do wind up buying $200 billion worth of them.

Mortgage bonds start with mortgages.

Mortgage bonds start with mortgages.

When a borrower takes out a 30-year fixed-rate loan, the lender usually isn't in it for the long haul.

When a borrower takes out a 30-year fixed-rate loan, the lender usually isn't in it for the long haul.

That's Chris Duncan, chief lending officer at LaSalle State Bank in Illinois.

That's Chris Duncan, chief lending officer at LaSalle State Bank in Illinois.

He says his bank usually doesn't want to hold on to long-term mortgages because they pay the bank a fixed interest rate for decades, and that would be a bad investment if interest rates were to rise.

He says his bank usually doesn't want to hold on to long-term mortgages because they pay the bank a fixed interest rate for decades, and that would be a bad investment if interest rates were to rise.

So instead, LaSalle State Bank, like most banks, sells off almost all of its long-term mortgages to the big government-backed mortgage companies.

So instead, LaSalle State Bank, like most banks, sells off almost all of its long-term mortgages to the big government-backed mortgage companies.