quick question about seller financing

[Michael Grigorashenko]

I'm reading a book called investing in real estate with low and no money down. Btw phenomenal book, there's a question I have.   When using seller financing method to buy a house and the house has a unpaid mortgage. The bank can ask me (the buyer) to pay in full, the mortgage that the seller (previous owner) didn't pay off, or the price that me and the buyer agreed upon?